Wind Chill Calculator

What is Wind Chill?

In winter, the temperature felt by the human body is typically lower than the actual ambient air temperature. This phenomenon is similar to the body feeling a higher temperature under high humidity conditions in the summer (refer to the Heat Index Calculator for further detail).

A surface, such as the skin on a person's body, loses heat through conduction, convection, and radiation. Although conduction and radiation are relevant to heat transfer, wind chill temperature is mostly a result of convection. Convection is defined as heat transfer due to the bulk movement of molecules within fluids such as gases and liquids (in this case, wind).

Essentially, as the air around a body moves, it blows away the thin layer of warm air surrounding the body, allowing cooler air to replace it. The faster the wind speed, the faster the surface cools. The physiological response of the body to an increased rate of heat loss is the generation of more heat to maintain surface temperature, resulting in the brain's perception of a lower temperature.

How to Calculate Wind Chill

Because wind chill temperature is not an exact physical science but a measure of human perception, weather services in different countries use slightly different standards relevant to their particular region. This calculator uses the official formula developed by the National Weather Service (NWS) in the United States.

Health Risks: Frostbite

Frostbite can occur when skin or other tissue is exposed to low temperatures. Usually, the first signs of frostbite involve numbness, discoloration of the skin, and feeling cold, typically in the extremities of the body. How quickly frostbite occurs is highly dependent on the wind chill temperature and the level of exposure.

Stages of Frostbite

• First-degree frostbite (Frostnip): Superficial damage that usually isn't permanent. Numbness and loss of sensation in the skin with possible swelling. Skin may slough off in the coming weeks.
• Second-degree frostbite: Blisters form and the surface of the skin hardens. Blistered skin dries, blackens, and peels. Possible permanent cold sensitivity and numbness.
• Third-degree frostbite: Tissue below the skin freezes. Blisters and bluish discoloration occur. Blackened crust develops while pain persists in the coming weeks. Long term damage to growth plates and ulceration can occur.
• Fourth-degree frostbite: Tendon, bone, and muscle are affected. Hard skin texture and a colorless appearance result. Re-warming occurs without pain. Skin later becomes black and mummified, and permanent damage may result in amputation.

Health Risks: Hypothermia

Hypothermia occurs when the body dissipates more heat than it can generate or absorb, leading to a dangerous reduction in core body temperature. In humans, hypothermia is defined as a core temperature below 95.0°F (35.0°C). Symptoms range from mild shivering to cardiac arrest.

• Mild hypothermia: Shivering, increased heart and respiratory rate, increased blood pressure, and mental confusion.
• Moderate hypothermia: Amnesia, slurred speech, loss of fine motor skills, and decreased reflexes.
• Severe hypothermia: Physiological systems start to fail, resulting in decreased heart rate, respiratory rate, and blood pressure. Victims may exhibit "paradoxical undressing" (taking off clothes due to disorientation) or "terminal burrowing" (entering small, enclosed spaces).

How to Dress Warmly for Winter Weather

Frostbite and hypothermia can lead to serious permanent, and sometimes life-threatening complications. Always dress with the wind chill (not just the thermometer temperature) in mind.

• 32 to 15°F (0 to -10°C): Dress warmly. A winter coat, gloves, and hat are required.
• 15 to -15°F (-10 to -25°C): Risk of hypothermia if outside for long periods. Dress in layers. A thin, wicking layer to remove perspiration from the skin, followed by a thicker layer of fleece or wool. The outer layer should be wind-resistant. Wear a warm hat, mittens, and a scarf.
• -15 to -50°F (-25 to -45°C): High risk of frostbite on exposed skin. Cover all exposed skin, particularly the face and hands. Limit outdoor activities to short periods of time.
• -50°F (-45°C) and colder: Outdoor conditions are exceptionally hazardous. Exposed skin may freeze in less than two minutes. Stay indoors.