Fundamentals of Temperature
How much do we really know and understand about heat stress?
Scientists and physicians actually know a great amount about heat stress and thermoregulation. Much of the current knowledge on the subject stems from research performed in hospitals, universities, and government and military agencies within the past century.
What do I have to do to regulate my body temperature correctly?
Because humans are homeotherms – meaning that we maintain a stable, “warm-blooded” body temperature regardless of the temperature of our environment – most of the time we don’t have to do anything at all. Our bodies are completely capable of releasing heat on a hot day or conserving heat on a cool day.
How efficient is my body regulating and maintaining temperature?
The body is able to maintain its temperature with incredible accuracy and precision. This means that not only is temperature kept within a very small range, but it is also able to stay within this range with little to no variation. The thermoregulatory system is also extremely fast and efficient and begins to adjust how heat is distributed, dissipated, or maintained within seconds of beginning exercise, changing posture, and even waking up.
What actually controls my body temperature?
The part of the body responsible for regulating body temperature is a portion of the brain called the hypothalamus, which begins functioning around birth. It integrates blood temperature, core temperature (gut and visceral organs) and peripheral temperature (skin and limbs) into one thermoregulatory response. The hypothalamus also has a role in raising body temperature during fever.
Do all animals of the same species always have the same body temperature?
Within species, normal body temperature will be kept stable within a finite ranger. The actual temperature of the animal will fluctuate depending upon any number of factors relating to the individual, such as health status, physiological state, environmental adaptations, and even the time of day.
Why does body temperature vary instead of keeping at one constant temperature?
The circadian rhythm is the biological phenomenon that dictates and changes body temperature according to the time of day. In humans, the body begins to cool around midnight and reaches the coolest temperature around 3:30am. Body temperature then begins to rise again in the morning and reaches its warmest point around 3:30pm. Temperature may fluctuate as much as 2 degrees Fahrenheit during this cycle.
Do people from extreme hot or cold environments have better adapted thermoregulatory mechanisms?
Regardless of where someone is born, the basic thermoregulatory mechanisms encoded in our genes are the same. There is no heritable biological adaptation for life in an extreme environment that we know of. However, that is not to say that cultural adjustments or behavioral modifications don’t have an effect. The best example is people living in the very far North: even though their bodies are no better adapted to arctic temperatures than someone from the equator, they survive because they wear heavy clothes.
Do children have different thermoregulatory mechanisms than adults?
Children do succumb to heat stress and cold stress more easily than adult. This is not because they have different thermoregulatory mechanisms, but because they are so much smaller. As a result from the discrepancies in mass, heat permeates into and dissipates out of smaller objects much more quickly than large objects. Though their bodies have the same capabilities as adults, their small size simply makes them more susceptible.
What is the difference between "stress" and "strain?"
In biology, a stress is any physical factor that produces a change in the way the body operates. Strain, meanwhile, is measured as the body’s response to that stress. For example, if two individuals are exposed to the same temperature, the stress on their body is equal. However, if one individual is wearing heavier clothing, the strain on his/her body will be much greater.
Can heat stress or cold stress be distinguished simply by measuring temperature and humidity?
Measuring temperature and humidity will provide a good indication of how animals may react to a certain environment, but cannot tell anything about how a specific individual will react. Disease, physiological state, degree of insulation, and even size can influence the degree of stress the animal will experience. Because of this, it is important to recognize that two individuals in the exact same environment will not always suffer the same amount of stress.
How does the body actually gain or lose heat? Does it gain or lose cold in the same way?
To begin, we need to understand that “cold” is not a physical phenomenon. Instead, cold is simply a term used to describe an absence of heat. The main processes of heat transfer for both gaining and losing heat are conduction, convection, and radiation. Heat can also be lost through evaporation and gained through the normal metabolic processes that are required to sustain life.
What are the factors that determine just how much heat is exchanged through conduction?
Surface area, temperature difference, time of contact, and material of the objects can all influence the degree of heat transfer between two objects via conduction. Temperature transfer will increase with a greater surface area, larger temperature difference, and a longer duration of contact between the objects. Additionally, certain objects, such as metals, conduct heat very well and will transfer heat easily. Other objects, such as wood, have lower conductance and do not transfer heat
What does "thermal conductivity" mean? What about "effective thermal conductivity?"
Thermal conductivity is a term used to describe how efficient an object’s conductive properties are, i.e. how well the object transfers heat through conductance. When measuring thermal conductivity, a higher value means that the object conducts heat very well, while a lower value means that the material is a poor conductor. Thermal conductivity is used when describing objects that are pure in nature, while effective thermal conductivity is used when the object in question is composed of multiple elemental materials.
When I place my hand on a metal desk, it feels cold. But is is actually cold?
Due to the properties of thermal conductance, any difference in temperature between two objects will result in a net flow of heat from the warmer to the cooler – if your hand is warmer than the desk, the desk will feel cold to you because you are actively transferring heat to it. If the object is an efficient conductor, it may feel relatively warmer or cooler. Therefore, it is very difficult to determine the exact temperature of an object just by touching it.
• Common Heat Exposure Questions • To the Top
Can repeated heat stress have long term effects?
As long as you deal with the heat stress on a day to day basis, there is no evidence to support long term health effects.
Is the heat from the sun produced by the same rays that result in a tan?
No, the rays that produce the warm feeling you get from standing in the sun are infrared rays. The rays that produce a tan are from the ultraviolet part of the spectrum.
Do sweat glands rid the body of harmful material?
Sweat glands do not play a significant role in excreting bodily materials. Although some chemicals from foods you consume can appear in sweat, the concentrations are too low to make a significant difference.
Why does the same temperature feel different at different humidity levels?
It is more difficult for the sweat to evaporate off your skin when humidity levels are high, making you feel sticky and uncomfortable. The skin also absorbs water from the air when there are high humidity levels.
How does "insensible" water loss occur?
Insensible water loss occurs when you lose water through your skin without sweating.
Why don't I always sweat when I am hot?
Chances are you are sweating. The water from your skin is just evaporating at the same rate it is being secreted.
Can I lower my body heat by drinking hot liquids on a hot day?
Although drinking hot liquids can increase sweating on the face, head and neck, it is usually not enough to cause any dramatic change in body temperature regulation.
Is salt an important addition to my diet in the summertime?
Although salt is important for proper health, additional salt does not need to be added to the diet during the summertime. There is enough salt readily available in our normal diets.
Does my dog or cat require extra salt in their diet during periods of hot weather?
No, since dogs and cats lose heat through panting, not sweating, they do not lose as much salt as humans do during temperature regulation. The salts lost during normal excretion of urine and feces do need to be replaced, but adequate amounts are found in commercial dog and cat foods.
How does the coat of a furred animal help it stay cool?
Since animals do not rely on sweating to lose heat, the fur coat protects the animals from radiative heat gains and warming from convection without reducing the amount of heat lost from evaporation.
Is It better to completely shave off my dogs coat in the summertime or leave it?
It is better to leave the dog’s coat on during the summertime than completely shave it off. The fur coat can actually help protect the dog against extreme heat stress.
How do I take care of my pet in the Summertime?
Providing your pet with plenty of clean, fresh and cool (not cold) water is essential. Shade should also be provided, whether natural or through use of a dog house or some sort of covering. If a dog house is used make sure the door is propped open to promote good airflow. Never leave your pet in the car on a warm (not even hot) day. The temperature within a car can rise to deadly levels within minutes. If your pet is unconscious, cover the fur with cool water, fan it and get it to the nearest vet.
Do people with spinal cord injuries have special needs to stay cool in hot weather?
The part of the brain responsible for temperature regulation still functions in people with spinal cord injuries. They may, however, have reduced blood flow and sweating in the areas below the injury. Individuals with spinal cord injuries may also have loss of sensation in certain areas, compromising their ability to sense the heat. As a result, care should be taken around hot objects, for instance metal buckles in a hot car and reducing the amount of time the person spends in direct sunlight.
A lot of people wear jogging suits to lose weight by increasing sweat rate. Is this a good idea?>
This is not a good strategy. The jogging suit prevents the sweat from evaporating preventing the body from cooling. This results in an increase in body temperature. Also the weight lost from sweating is immediately regained once the water is replaced.
Do children require special precautions during high levels of heat?
Very small children, such as infants do require extra attention in the heat and should be observed closely. Although they have many of the same heat loss mechanisms, their small body weight allows them to heat up faster, reaching thermal stress quicker than an adult. Loose fitting clothing, good air flow and shade are essential.
Do the elderly have special needs to stay cool?
Some elderly people have reduced ability to sense hot or cold stimuli on their skin and are thus more susceptible to heat stress. During hot weather, it is important to make sure a cool room or area is available to escape the heat.
When is hyperthermia useful?
When implemented by a trained physician, hyperthermia can be used to control a number of illnesses including venereal diseases, mental illness, arthritis and cancer.
Do obese people have a harder time staying cool than thin people?
Obese people may have a harder time reducing thermal stress than fit people. Individuals with extra body fat must do more work during the same activity than people with little excess body fat. This extra work increases body temperature. Also, fat is a thermal insulator and may reduce heat dissipation.
What is meant by the term "spiking fever?"
Sudden increases in body temperature that goes above that expected during a fever. If body temperature gets too high, the mechanisms for cooling may not be sufficient and body temperature will continue to increase.
Can beer replace the water and salts I lose from sweating?
Although beer does contain the water and salts lost during high heat, the alcohol makes it a poor choice during any thermal stress situation. The alcohol causes the kidneys to rid the body of more water than what was actually consumed, resulting in a dehydration effect.
Are there any medications that can help me stay cool during high heat?
There are no drugs that help increase the body’s ability to stay cool during hot weather. However there are some that will impair this function. It is important to check with a physician before taking any medications during periods of high heat.
Aspirin can help reduce a fever.
can it also help keep my body cool in the heat?
When body temperature rises from heat stress, is that the same as having a fever?
No, the increase in body temperature due to heat stress is caused by the body gaining heat from the environment or some activity faster than it can lose it. A fever results when the body is trying to rid itself of some harmful organism or pathogen and thus regulates at a higher than normal temperature.
I drink water all day when I am in the heat, but sometimes I feel nauseated and have muscle cramps after being home for a few hours. Why is that?
The cramps and nausea could be signs that although you are replacing the water lost from time spent in the heat, you are not adequately replacing the body salts lost. If you spend a lot of time in the heat sweating, a drink containing higher levels of electrolytes may be necessary to replace both the water and salts excreted during sweating.
Are salt tablets needed on a hot day?
Probably not, most diets contain enough salt that supplements are not required.
Can any beverage replace the water I lose on a hot day?
Although small amounts of other beverages on a hot day will not pose any health issues, completely replacing water with alternative drinks is not a healthy solution to dealing with the heat. Other drinks such as lemonade and soft drinks are often high in sugar and thus are not healthy in large amounts whether heat stressed or not.
• Common Cold Exposure Questions • To the Top
How do you measure how cold it really is?
Air temperature, in a lot of ways, is the least reliable single indicator of cold stress. Remember that it depends on more than just environmental characteristics. The insulative abilities of your clothing, how they are being worn, and your physical activity are all factors. It also depends on individual health, body composition, and your personal experience in the cold. Conditioning is a major factor in your response to cold weather.
What is the difference between a person experiencing cold stress with a heavy coat on, gloves, scarf, hat and boots compared to someone wearing a t-shirt and shorts?
Although scientists have collected data on how cold and windy a day is, they have also collected temperature, air flow, and humidity within and under a person’s clothing. It is thought, an animal’s survival in dealing with cold or heat stress is a result of the microenvironment they make for themselves. The person who wore the layers helped to create a thermal microenvironment much in the same way a raccoon forms a cozy insulated nest in a tree.
How do your clothes help keep you warm during cold stress?
Whether it is fur, fabric, feathers, or any combination of artificial and natural fibers, it all depends on the amount of air that is trapped near the skin. Feathers, fur, and wool give about 22 times more insulation than skin and muscle for the same thickness because they trap air. Heavily insulated body covering is just as effective in reducing heat loss. The material that traps the air is not as important as the volume of air that it can maintain.
If the insulative ability of clothing is due to the air it traps, then wearing more clothing should allow you to stay warmer?
The more layers you wear, the more insulation you add to your bare skin. Eventually you will reach a point of diminishing returns by adding additional clothes, creating a large surface area. There is a theoretical point at which you begin to lose more heat due to the increase in surface area than you gain because of the added insulation of the layers. However, wearing several layers of clothes gives you the option to remove some of them when temperature climbs.
If fur is such a good insulatorit traps air, how is it that an animal's thick fur in the winter does not make it heat stressed as it moves around and has to get rid of body heat?
It does. Animals with fur make their own adjustments in the insulative quality of their coats but in a different way from humans.
How can fur keep an animal, such as a beaver, warm when it goes in and out of the water?
There are two ways, both of which are attributed to trapping fluids in the fur. The animal is able to trap air and water beneath the fur. The insulative quality of the trapped water is about 30 times less effective than air trapped in the fur, but is at least one hundred times more effective for controlling body temperature than having the bare skin exposed to the cold, flowing water.
What is a microenvironment and why is it important?
Constructing a comfortable microenvironment like a well-insulated nest or den helps to get the animal out of the direct cold, for periods of time. Animals with fur that spend most of their time on land have dense fur coats to keep them thermally stable in the winter. Growing a heavier fur coat gives external insulation.
My dog gets a thicker coat in the beginning of winter each year and then sheds it a couple of months later even though she is kept in the house almost all of the time. How does she get cold enough to cause the new fur to grow for the winter?
Animals including humans as well as plants respond to seasonal light cycles with many different hormonal and physical responses. The shortening of the day as winter approaches is the stimulus for the fur growth with your pet. The light induced stimulation gives a valuable means of getting ready for cold weather.
I just bought a new wool jacket that is warm when there is no wind, but is so loosely woven that I get cold even if there is only a slight breeze. I could wear a wind-proof coat on top of it, but is there anything else I can do?
No, but there are ways you can take advantage of these properties of the coat. As the blowing air penetrates into the loosely woven fibers, it changes the microenvironment of the air layer trapped beneath. This air layer is responsible for determining its insulative quality. If you wear a tightly woven covering over, it would help to prevent this.
How can you increase your metabolic heat production during exposure to cold weather, other than shivering or exercise?
The process is called “non-shivering thermogenesis” which implies there is a production of heat without shivering. A particular type of fat known as “brown fat” is used to generate heat at specific times.
Okay so I just had my house insulated. Why does the house feel warmer even at the same temperature?
Your comfort level is dependent on the net effect of heat exchange by conduction, convection, radiation and heat loss by evaporation. By insulating the ceiling and walls of the house, it reduced the rate at which it loses heat by conduction to the outside.
What is "wind-chill?"
Despite what you might hear on a weather report, wind chill is not a measure of how cold the air feels, rather, a calculation of how cold it would have to be to cause the same rate of heat loss from your skin if there were no wind blowing. Wind chill was developed when two explorers, spending winter in the Antarctic, started measuring how long it took water to freeze in plastic containers hanging in the wind. Currently it is calculated based on how much heat is lost from human skin in a windy
What is "relative Humidity?"
Relative humidity is important to know in both hot and cold weather but for different reasons. When air temperature rises above 85F, losing heat depends on evaporating the sweat from your skin. Relative humidity becomes a critical factor in thermal safety when air temperature reaches 95F. It must stay low enough for evaporative cooling because that is the only avenue of heat loss in which we can survive.
Why is it that it feels colder in fall and spring when it is raining and the humidity is high? Does the higher humidity really cause you to lose more heat?
Studies have proven that despite how much colder we may feel on a cold-wet day, we actually do not lose any more heat than we do on a cold-dry day. Air conducts heat only slightly better when the humidity is high. You feel cooler because the air’s humidity affects our perceptions of temperature but not the level of cold stress.
Last winter my left hand became red, swollen and painful. The doctor told me that I developed chilburns. What are they and does it mean I had frostbite?
No, this is not frostbite but is known as a non-freezing cold injury. Frostbite is when ice crystals form in the tissue. Chilblains occur when tissue gets cold and stays that way for a long enough period of time to temporarily affect your local circulation.
Are there different degrees of frostbite? What are they and how are they related?
Yes, frostbite is graded on a scale in degrees of severity, in the same way as burn injuries. First-degree frostbite is the least severe and results in the loss of only superficial tissue. Second-degree occurs when ice crystals form in the tissue. Third-degree frostbite is the most serious and occurs when the tissue has become completely frozen through the extremity.
Today when I was out building a snowman, my fingers got extremely cold at first, but after a while they became so warm I no longer needed to wear gloves. Why is this?
What probably happened was known as “cold-induced vasodilatation” response. When first exposed to the cold, blood flow to the fingers was reduced below the normal level at room temperature. The body reduces blood flow which causes heat delivery to decrease in order to help conserve heat.
A fit person might need to wear a heavier winter coat when it is cold compared to a person whi is overweight and seems to be more comfortable in the colder climates. Why?
An overweight person produces more heat when they move around. The extra pounds require them to work more than the thinner person. It’s this heat which delays the feeling of being cold. Body fat is a great thermal insulator and restricts heat loss.
I spend a lot of time and money at health stores but have never seen a pill or vitamin which claims they will help keep you warm in the winter. How can I find products available to do this?
Don’t waste your time! There are not any available. If you would like to increase your ability to withstand cold weather, try to develop a nutritional plan and improve your level of physical fitness. Instead of searching for a magic pill, design a healthy program that fits your body type.
How much does jogging increase metabolic rate?
Fast running increases metabolic rate by how many calories per hour?
900 to 1000%
When you come in from the cold do you warm faster by leaving on your winter coat or taking off your coat, gloves and hat?
This depends on how warm your house is. A warm home will heat you up faster without your coat on. Otherwise, you have to generate enough body heat to warm the coat insulation which could take a while and cause you to use up a lot of extra energy.
Does drinking alcohol allow you to stay warm in the cold? I have heard that it contains a lot of calories?
Actually the few calories in alcohol are rapidly metabolized. Alcohol lowers metabolic rate and eventually body temperature. Alcohol also lowers your perception of temperature and relaxes your defenses against cold and heat. You feel warm while your body temperature is dropping and this puts you in a dangerous situation in the cold.
Why does drinking alcohol cause you to put on weight? Is it due to the extra calories?
The number of calories in alcohol really is not the problem. Drinking alcohol makes you hungry and you overeat. This is where the extra calories come from.
Should I wear a hat when I go out in the cold? Why is my hair not enough?
Your head is a great radiator of heat because blood flow to regions like the mouth, nose and ears do not change with temperature. This means that when the temperature gradient between the skin and air is very large there is tremendous heat loss.
How does the shape of my head and structures like the nose and ears affect heat lose?
Shape and size has a large effect on heat loss. Small objects lose more heat than large objects just based on size. So ears would dissipate more heat than the top of the head. Thin, narrow objects lose more heat than thick objects. So the ears release more heat than the trunk of the body. Likewise, the arms and legs lose more heat than the trunk.
What type of hat should you wear in the cold?
The more air it traps the better it insulates. Also, the closer that it traps air to the skin the better. Ventilation is important as well. If the hat traps a lot of moisture and it builds up, it will decrease its ability to insulate. Also, the hat should not restrict blood flow to the head. If blood flow is reduced, it decreases the warming of the head.
Why is it important for newborn babies to wear a stcking cap?
First of all, small objects release more heat than large objects by size alone. Also the thinner shape allows babies to lose more heat than an adult. Second, the metabolic rate of a newborn is lower than that of an adult, preventing them from replacing all the heat that they could potentially lose from the head.
What sort of clothes should an infant wear in the cold?
Not only should they be well ventilated but well insulated as well. Also the clothes should be easily opened or removed when in a warm environment, such as a mall. Overheating (which can result from sweating and getting clothes damp) is as large a problem as getting too cold.
We have a large dog that spends its entire time outdoors even in very cold weather. It has a dog house but what else should it have?
Most large pets are ok in the cold if they are in good health, out of the wind (e.g., windbreaks), and have access to unfrozen water. The doghouse should be free of water leaks and wind drafts and have an insulated bottom.
What is the amount of sensory input that we receive per second?
It is about 40 billion sensory inputs per second and we are consciously aware of a maximum of 40.
You have a small dog that stays inside most of the time. When there is snow on the gorund, it seems like the snow hurts his feet. But the veterinarian says don't worry about this. What should you do?
Dogs, cats, and other animals (even humans) reduce blood flow to feet and toes in the cold to conserve body heat. This can be uncomfortable and painful even to us. Pets experience a similar thing.
What are specific problems with pets in the winter?
Balls of ice may form between the toes in the deep cold of winter and can be harmful and should be removed. Frostbite and hypothermia may also be an issue during a very cold winter. Animals with short fur and older animals are particularly susceptible to the cold and should be carefully watched.
My cousin has had to use a wheelchair for the last 6 year due to spinal injury that resulted from a car accident. Does he have to be careful in the cold regarding his control of body temperature?
The effects of spinal injury can vary widely and a physician will have to be consulted for specific details. However, the reduced exercise level from being in a wheelchair reduces metabolism and heat production making him more susceptible to the cold. If he is unable to decrease blood flow to arms and legs in the cold, then he will lose more heat.
What special care is needed for my 85 year old grandfather in the cold? He lives alone and has been going downhill over the last few years. Reduced activity and poor health and could lead to reduced metabolic rate and heat production.
How cold do you have to get to be classified as hypothermic?
Body temperature and heat content have to be lower than normal to be considered hypothermic. Just being severely chilled and uncomfortable with extreme shivering does not mean you are hypothermic. Although overall body heat content is low, the deep body temperature may be within the normal range.
Why is hypothermia such a severe problem?
Often the individual doesn’t realize they are hypothermic. They may not shiver or complain of the cold. But they may be dizzy, disoriented and confused. They may be at the threshold for hypothermia and susceptible to falling into a deeper state.
What are the concerns if deep body temperature is below 90F?
This is a medical emergency and immediate medical care is needed. Between 80 and 90F, the individual may appear sleepy and not respond when spoken to. They will not shiver and the muscles will be stiff. A person with profound hypothermia may appear dead even to professionals with no detectable pulse, slow and shallow breathing with stiff arms. Shining a bright light into their eyes produces no papillary response.
How does hypothermia develop in a person?
It occurs when body heat content and temperature fall below the normal range. Heat loss exceeds heat gained from the environment and produced by the individual. Also, intoxicated individuals or those on depressants could be at an increased risk of becoming hypothermic.
Do I run the risk of damaging my lungs if I breathe in very cold air?
No, very little heat is required to increase the temperature of the air that you take in even when the temperature is as low as -30F. In this environment, there is no risk of cooling the lungs, forming ice crystals in the lungs, or having frostbite in this area.
Are there any problems breathing in cold air?
Yes there are. It causes a reflex similar to that which occurs when breathing in noxious fumes. First you gag, then your throat closes off and you cannot take in a deep breath. This reflex is started by a drop in tissue temperature and is partly due to drying of the nasal area and back of the mouth. Cupping the hands in front of the face, and breathing through a scarf over the nose and mouth helps to preheat the air to reduce this response.
If I want to jog in cold weather what precautions should I take?
The biggest problem is the loss of body heat. Also, wetting the clothes from sweating could present a problem. You will need shoes with some insulation on the bottom to prevent heat loss to the ground. You should limit swinging your arms and moving your legs to reduce heat loss by convection. Protect the narrow parts of your body like the hands, feet, arms, and legs against the cold using clothing that is not penetrated by the air. These areas do not sweat and so there is no problem here with moisture buildup.
When I go out in the cold on a windy day my fingers get so cold and ache after only 30 minutes. Gloves do not seem to work. What else can I do?
Reduced blood flow to the fingers and toes is one line of defense to reduce heat loss in the cold. The rate of this response and level of response varies a lot across humans and other animals. You should likely add more insulation to these areas and consult with a physician.
Why do I get more colds and flu in the winter? How does a cold temperature decrease my resistance to infections?
Cold by itself doesn’t increase susceptibility to common winter ailments. That is a myth. Here are other things that could be happening: 1. we spend more time indoors in the winter and therefore are in contact with more people and exposure to disease organisms. 2. Percent relative humidity of the air is lower in the winter than in the summer because cold air can hold less moisture than warm air.
What is the best type of clothing to wear in the winter?
This depends on what you plan to do and the conditions that you plan to do it in. Trying to keep warm by exercising or shivering is not suitable for long-term exposure to cold. The most important thing is to decrease heat loss and capture most of the heat that might leave the body without holding onto moisture.
How do I know if I have a frozen finger or toe? Is there a shooting pain when ice crystals form?
The danger of frostbite is that you will not know when it happens. As with hypothermia, there is no consistent signal. Frostbite can occur with rapid heat loss and when air temperature is 20F or below. A windy environment puts you in greater danger. You are also in greater danger if water is evaporating from the skin.
What do you do if frostbite occurs?
If this happens to your fingers, remove the glove and put your fingers in your armpit or against your body until they rewarm. If this happens to your toes, do not walk on them and find shelter, remove your shoes and socks and warm your toes by holding them between your hands. Do not rub them.
How do you check for frostbite?
If the extremity is waxy-white, cold and hard to the touch, without sensation, some amount of frostbite is certain. Find a physician as soon as possible.
Why do I sweat when I shovel snow in the cold?
Sweating doesn’t help you in the cold. This is simply a reflex. The body is anticipating the load and responds after a few minutes to the first increase in warmth. You can loosen or remove the outer layer of clothing, keeping the ears and fingers covered. The goal is to keep air flowing through clothing and over the skin so the sweat evaporates.