What is Windchill? Basically, it combines the cooling effect of temperature and wind, driving down the “perceived” temperature. Interestingly, the wind does not change the temperature of the air; it’s changing your body’s temperature. See the Windchill Chart, how windchill is calculated, and how it all works.
What is Windchill?
The Windchill Temperature Index is a “measure of the combined cooling effect of wind and temperature.”
Let’s explain: Have you ever noticed that you “feel” colder in the winter if the wind blows? You’re not imagining this! How cold it “feels” is not just about the temperature. It’s also about wind speed. The body is cooled faster as the wind speed increases, causing the skin temperature to drop.
Why? Our body keeps a “buffer” or thick layer of air next to our skin to help us regulate our body temperature (maintaining 98.6°F). Think of this buffer as an insulating jacket! A strong wind can disrupt this buffer layer, making us feel colder.
When the wind picks up speed, it draws more heat away, so if your skin is exposed to the wind, your body will cool faster than it would have on a still day.
Combining freezing temperatures with a frigid wind increases the danger of frostbite and hypothermia. In northern climates, it’s not uncommon to hear wind chill warnings where exposed flesh can freeze in less than a minute.
Windchill Temperature Chart
The wind chill chart isn’t technically measuring “how cold it feels,” even though your body will certainly notice it’s colder. It reflects the rate of heat loss on exposed skin.
Wind chill IS a good indicator of how long it will take for hypothermia or frostbite to occur.
The Windchill Temperature (WCT) chart below was created in 2001/2002 by Environment Canada (EC) and the U.S. National Weather Service (NWS). It replaced the prior 1945 Siple and Passel Index, created during a United States Antarctic Expedition from 1939 to 1941.
The Windchill Temperature (WCT ) index gives the perceived temperature equivalent for the combination of cold air and wind. It shows air temperature in degrees Fahrenheit and wind speed in miles per hour. Here’s how to convert from Fahrenheit to Celsius.
The chart also includes a frostbite indicator, showing the points where temperature, wind speed, and exposure time will produce frostbite in humans. Each of the three shaded areas shows how long a person can be exposed before frostbite develops. For example, a temperature of 0°F and a wind speed of 15 mph will produce a wind chill temperature of -19°F. Under these conditions, exposed skin can freeze in 30 minutes.
Windchill Temperature ChartWind
Speed
(mph) | Temperature (°F) |
|---|
| Calm | 35 | 30 | 25 | 20 | 15 | 10 | 5 | 0 | -5 | -10 | -15 | -20 | -25 | -30 | -35 |
|---|
| 5 | 31 | 25 | 19 | 13 | 7 | 1 | -5 | -11 | -16 | -22 | -28 | -34 | -40 | -46 | -52 |
|---|
| 10 | 27 | 21 | 15 | 9 | 3 | -4 | -10 | -16 | -22 | -28 | -35 | -41 | -47 | -53 | -59 |
|---|
| 15 | 25 | 19 | 13 | 6 | 0 | -7 | -13 | -19 | -26 | -32 | -39 | -45 | -51 | -58 | -64 |
|---|
| 20 | 24 | 17 | 11 | 4 | -2 | -9 | -15 | -22 | -29 | -35 | -42 | -48 | -55 | -61 | -68 |
|---|
| 25 | 23 | 16 | 9 | 3 | -4 | -11 | -17 | -24 | -31 | -37 | -44 | -51 | -58 | -64 | -71 |
|---|
| 30 | 22 | 15 | 8 | 1 | -5 | -12 | -19 | -26 | -33 | -39 | -46 | -53 | -60 | -67 | -73 |
|---|
| 35 | 21 | 14 | 7 | 0 | -7 | -14 | -21 | -27 | -34 | -41 | -48 | -55 | -62 | -69 | -76 |
|---|
| 40 | 20 | 13 | 6 | -1 | -8 | -15 | -22 | -29 | -36 | -43 | -50 | -57 | -64 | -71 | -78 |
|---|
| 45 | 19 | 12 | 5 | -2 | -9 | -16 | -23 | -30 | -37 | -44 | -51 | -58 | -65 | -72 | -79 |
|---|
| 50 | 19 | 12 | 4 | -3 | -10 | -17 | -24 | -31 | -38 | -45 | -52 | -60 | -67 | -74 | -81 |
|---|
| 55 | 18 | 11 | 4 | -3 | -11 | -18 | -25 | -32 | -39 | -46 | -54 | -61 | -68 | -75 | -82 |
|---|
| 60 | 17 | 10 | 3 | -4 | -11 | -19 | -26 | -33 | -40 | -48 | -55 | -62 | -69 | -76 | -84 |
|---|
| Frostbite occurs in: | 30 minutes | 10 minutes | 5 minutes |
For example, when the temperature is 15°F and the wind speed is 30 miles per hour, the windchill, or how cold it feels, is -5°F.
How to Calculate Windchill
The windchill chart above was designed to calculate how cold air feels on human skin accurately. The index is based on heat loss from exposed skin and was tested on human subjects’ faces.
For those interested, Windchill is a basic Algebraic formula:
The Fahrenheit version of the equation looks like this:
Wind Chill = 35.74 + 0.6215T – 35.75(V^0.16) + 0.4275T(V^0.16)
T is the air temperature in degrees Fahrenheit, and V is the wind speed in miles per hour.
The above formula makes some assumptions: that your exposed face is roughly five feet off the ground, it’s night, and you’re walking directly into the wind in an open field at three mph.
While that formula may not reflect your reality, and you could date the way it’s calculated, the basic concept is important: Cold winds will cause exposed skin to cool more quickly, and frostbite will happen more quickly. Pay attention when there are high winter winds!
Dangers of Windchill
- Frostbite: Windchill actually causes your body tissue to freeze! Frostbite in body tissue that has frozen and usually starts with the fingers, toes, tips of the nose, and ear lobes. If you lose feeling in these areas or they are turning pale or white, immediately get inside and get medical attention.
- Hypothermia: Hypothermia sets in when your body’s temperature drops too low. Uncontrollable shivering, disorientation, and incoherence are signs of this issue, and medical attention should be sought immediately. Learn about the signs of hypothermia.
In both cases, take care to rewarm the body very slowly.
Windchill Safety Tips
Be smart about windchill! Here are some common-sense safety tips:
- Listening to the weather station. Windchill Warnings are issued when wind chill temperatures are life-threatening. Windchill Advisories are issued when windchill temperatures are potentially hazardous.
- When there is low windchill, cover your exposed flesh, especially your face and hands! Consider a balaclava to cover your mouth and protect your lungs. Mittens are better than gloves.
- Wear layers of loose-fitting, warm clothing, as the layers will trap air and provide insulation. Your outer shell should be water-repellent and hooded.
- Always wear a hat.
- Read more tips on how to stay warm in the winter.
Check out the Beaufort Wind Scale to learn how to judge the speed of the wind!
