How to read Wind Chill Chart to stay comfortable outdoors

For sports and outdoor activities, we usually consider the wind chill in order to dress correctly for the different weather. In this article, we’ll analyze why the temperature on the thermometer often differs from your feelings and how to read Wind Chill Chart in order to stay comfortable outdoors in any weather and avoid hypothermia and frostbite.

What is wind chill?

The wind chill or the Wind Chill Factor is one of the indexes that characterize the feels like temperature, an indicator that includes not only air temperature but also air humidity and wind speed.

The Wind Chill Factor is how much the body temperature will drop, depending on the exposure to the wind. In other words, it shows how much heat the human body loses. The higher the wind speed, the faster the surface cools (including the human bodies).

(Humidity is not taken into account here, for this we have a Heat Index of the same feels like temperature.)

The Wind Chill Factor is always lower than the actual air temperature.

How Wind Chill Factor is calculated? Is there any formula?

There is no single way to calculate the Wind Chill Factor. It can be counted differently in meteorological services. The formulas for calculating this indicator are quite complicated. For example, the US National Weather Service of the NOAA uses this formula:

Wind Chill formula / NOAA

How to read Wind Chill chart?

There are also visual tables that can be used to calculate the Wind Chill value.

The Wind Chill Chart of the same NOAA displays air temperature and wind speed (in mph) along the axes. At their intersection, there’ll be a “feel of temperature” or the Wind Chill Factor. The background of the table is covered with different colors — they represent the time required for frostbite.

Wind Chill Chart. Valerya Milovanova / Windy.app

For example, with an air temperature of −15 degrees Fahrenheit and a wind speed of 20 mph, Wind Chill is −42 degrees and frostbite can occur in 10 minutes or less.

In 5 minutes, you can get frostbite even at a temperature of −10 degrees Fahrenheit, if the wind speed is 60 mph, and at a wind speed of only 15 mph, if the air temperature is −40.

Note that you can get frostbite even at above-zero temperatures: if the air temperature is 5 degrees and the wind speed is 30 mph, it occurs in half an hour.

Why is it important to know the Wind Chill Factor for my sport or outdoor activity?

Snowboarding or skiing at a temperature of −10 is quite comfortable, and even wind of 10 m/s (about 22 mph) does not greatly interfere with the rider when he is on the move. But just think that when you sit in an open lift cabin in such weather conditions, you already feel almost −37 degrees. When the lift stopped for almost 10 minutes in such a situation, you may urgently need a hot tea.

The same with fishing. It’s one thing to fish in complete calm when the temperature on the thermometer corresponds to the felt — temperature and it’s not difficult to dress for the weather. It’s another matter when it’s 30-35 Fahrenheit outside (it’s about 0 Celsius), and the wind blows 15 m/s this already feels like 19 Fahrenheit (or −7 Celsius). And this, consider, 2 different seasons — autumn and winter!

For water sports, the Wind Chill Factor is also very important. Whether you’re sailing a windsurf, kite, or racing yacht, strong winds will not only give you the opportunity to take a smaller sail and go faster but also force you to wear a warm wetsuit to protect yourself from the chilling wind. Don’t forget it.

Photo: Taneli-lahtinen / Unsplash

Snowkiting is a separate topic. For this sport, the wind is necessary, plus the rider always moves at a considerable speed — that is, the wind has a doubly cooling effect on him. That is, imagine that at a normal snowkiting speed of 10 m/s (22 mph), the rider is moving at a speed of at least 20 km/h (12 mph), i.e. a wind of 35 mph can blow in his face. And at an air temperature of 14 degrees Fahrenheit (-10 Celsius), it feels like −7 degrees Fahrenheit, i.e. −22 Celsius. Snowkiters cannot go out for a ride without special equipment.

For fans of winter jogging (running), it’s also important to remember that even a small minus like −5 degrees and a light wind up to 5 m/s already give a feeling of −16 degrees when combined, and these are already serious winter conditions that require careful selection of equipment.

Where to get Wind Chill Chart in Windy.app?

Windy.app has its own feels like temperature formula too, using both indicators depending on the weather conditions. We have a combination of Heat Index and Wind Chill Factor: at temp <50 °F (10 °C) we use wind chill, and at temp >80 °F (26.6 °C) — Heat Index. And for the average values, we consider wind, also. To get feels like temperature in Windy.app:

1. Open your favorite or the nearest sport to your current location.

2. Choose Lite Weather profile by an icon of the umbrella right to the weather forecast models on the spot screen.

3. Get feels like temperature for today:

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