Windchill Chart for the United States

Know When Frostbite and Hypothermia Might Occur

January 14, 2020
Icicles on Tree

This updated Wind Chill Chart helps you understand how cold it “feels” outside—by combining the cooling effect of temperature and wind. Also, see how wind chill is calculated and how to protect yourself from the danger of frostbite and hypothermia. 

What is Wind Chill?

The Wind Chill Temperature Index is a “measure of the combined cooling effect of wind and temperature.”

Let’s explain:  Ever noticed that you “feel” colder in the winter if the wind is blowing? You’re not imagining this! How cold it “feels” is not just about the temperature. It’s also about wind speed. As the wind speed increases, the body is cooled at a faster rate causing the skin temperature to drop.

Why? Our body keeps a “buffer” or think layer of air next to our skin to help us regulate our body temperature (maintaining 98.6°F). Think of this buffer like an insulating jacket! A strong wind can disrupt this buffer layer, making us feel colder. 

If you combine freezing temperatures with a frigid wind, the danger of frostbite and hypothermia increases. In northern climates, it’s not uncommon to hear wind chill warnings where exposed flesh can freeze in less than a minute.

Wind Chill Temperature Chart

The Wind Chill Temperature (WCT) chart below was created in 200½002 by the 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 in the 1939 to 1941.

The Wind Chill 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 on humans. Each of the three shaded area 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.

Wind Chill Temperature Chart

Wind
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

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 is Wind Chill Calculated

The windchill chart above was designed to accurately calculate how cold air feels on human skin. The index is based on heat loss from exposed skin was tested on human subjects’ faces. 

For those interested, the Wind Chill formula is:

WC = 35.74 + (0.6215 x T) – (35.75 x (v ^ 0.16)) + (0.4275 x T x (v ^ 0.16))

WC is the wind chill index in Fahrenheit, v is the wind speed in miles per hour and T is the temperature in Fahrenheit.

Dangers of Wind Chill

  • Wind chill actually cuases your body tisue to freeze! Frostbite is 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 area or they are turning pale or white, immediately get inside and get medical attention. 
  • Hypothermia happens when your body’s temperature drops too low; uncontrollable shivering, disorientation, and incoherence are signs of this issue and medical attention should be found immediately.

In both cases, take care to rewarm the body very slowly.

Windchill Safety Tips

Be smart about wind chill! Here are some common-sense safety tips:

  • Listening to the weather station. Wind Chill Warnings are issued when wind chill temperatures are life threatening. Wind Chill Advisories are issued when wind chill temperatures are potentially hazardous.
  • When there is low wind chill, 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.

Check out the Beaufort Wind Scale to learn how to judge the speed of the wind!

Source: 

Courtesy of the National Weather Service/NOAA