Sweating in cold weather seems contradictory since the body’s main goal in a chilly environment is to conserve heat. This seemingly paradoxical event occurs because sweating is not solely a response to hot surroundings; it is a mechanism triggered any time the body senses that its internal temperature is rising past a safe level. Whether the external air is frigid or warm, the body still retains the ability to overheat from the inside, forcing the cooling system to activate.
The Body’s Internal Thermostat
The control center for body temperature is a small region in the brain called the hypothalamus, which functions like a thermostat. This region constantly monitors the core temperature, aiming to maintain it within a narrow range, typically around 98.6°F (37°C). The hypothalamus does not primarily react to the temperature of the skin or the surrounding air but rather to the temperature of the blood circulating internally.
When sensors detect that the internal core temperature has surpassed its specific set point, the hypothalamus initiates cooling responses. One of the most effective cooling responses is the activation of the eccrine sweat glands, which are distributed across most of the body. Sweat then evaporates from the skin surface, a process that removes heat energy and lowers the internal temperature. This mechanism activates whenever internal overheating occurs, regardless of the chilly external conditions.
Metabolic Heat from Physical Exertion
Physical activity is one of the most frequent causes of sweating in cold weather because muscle work generates significant internal heat. During exertion like shoveling snow, hiking, or running, the body increases its metabolic rate to produce the energy molecule adenosine triphosphate (ATP). Heat is a byproduct of this energy production process, which can dramatically raise the core temperature.
Even in freezing air, the amount of heat generated by active muscles can quickly outpace the body’s ability to dissipate it through normal processes. A person engaging in vigorous activity can produce heat at a rate that requires the body to shed up to 0.7 to 1.5 liters of sweat per hour. This rapid internal temperature spike signals the hypothalamus that the body is in danger of overheating, demanding immediate cooling via sweat. If the body is fully covered to stay warm, the generated heat becomes trapped, forcing the cooling response to activate.
Trapped Heat from Insulation and Clothing
Another major contributor to cold-weather sweating is the over-insulation provided by heavy or numerous layers of clothing. Insulation works by trapping air close to the skin, which is beneficial for staying warm. However, wearing too many layers or garments that are not breathable prevents the body’s heat from escaping effectively.
This over-insulation creates a warm, humid microclimate directly next to the skin, even while the outermost layer is exposed to cold air. If the body is generating heat, the trapped air prevents the heat from dissipating. The hypothalamus detects this increased heat retention and triggers sweating to cool the skin surface within the layers. To manage this, using a layering system with a moisture-wicking base layer and a breathable outer shell is recommended, allowing layers to be adjusted or vented to prevent excessive heat buildup.
Sweating Triggered by Stress or Illness
Sweating in cold environments can also be caused by factors unrelated to physical exertion, such as emotional stress or illness. Stress and anxiety trigger the body’s “fight-or-flight” response, causing a surge of adrenaline. This hormonal release stimulates the sweat glands, particularly the apocrine glands in the armpits and groin, but also the eccrine glands across the body, in a process independent of core temperature regulation.
Illness causing a fever also leads to sweating, even when a person feels cold. Fever occurs when the hypothalamus intentionally raises the body’s thermostat set point in response to pyrogens released by the immune system. After the body successfully fights the infection, the hypothalamus resets the temperature set point back to normal. The body then needs to rapidly shed the accumulated heat to meet this new, lower target, which results in a profuse “breaking” sweat that often makes the person feel clammy and cold.