What Does “Wind Chill” Mean and How is it Calculated?
Thursday started off brutally cold in Chicago, with wind chills dipping below zero. But what exactly does that mean and how is it calculated?
A wind chill is the “measure of how cold the air feels on your skin,” according to NBC 5 Storm Team Meteorologist Kevin Jeanes. “How cold it is, plus how strong the winds are,” he added.
So how do you determine just how cold it feels? The equation isn’t quite as simple.
How to Calculate Wind Chills
According to the National Weather Service, “wind chill is based on the rate of heat loss from exposed skin caused by wind and cold.”
“As the wind increases, it draws heat from the body, driving down skin temperature and eventually the internal body temperature. Therefore, the wind makes it FEEL much colder,” the NWS reports. “If the temperature is 0°F and the wind is blowing at 15 mph, the wind chill is -19°F. At this wind chill temperature, exposed skin can freeze in 30 minutes.”
The formula used to calculate wind chill is:
35.74 + 0.6215T – 35.75 (V^0.16) + 0.4275T(V^0.16) = Wind chill
In this equation, the “T” variable represents the air temperature, while the “V” variable represents the wind speed.
The formula also accounts for heat transfer theory and skin tissue resistance, according to the NWS.
For example, an air temperature of 10 degrees, and a wind speed of 25 miles per hour will create a wind chill of approximately minus-11 degrees Fahrenheit.
“Our bodies naturally give off heat,” Jeanes explained. “The air just around our body warms up, but when when the wind picks up, that removes the heat. So our body heat that it naturally gives off isn’t warming us anymore. It isn’t keeping us insulated.”
How Wind Chill is Calculated
According to officials, the formula takes into account a measurement of the wind speed as measured at the average height of a human face, which is five feet. It also takes into account that a typical anemometer, a device used to measure wind speed, is placed 33 feet in the air.
In order for wind chill to be calculated, the air temperature must be at or below 40 degrees Fahrenheit, the NWS said. Finally, the formula assumes that measurements are taken at night, with no sunlight influencing the “feels-like” temperature.
Frequently Asked Questions
Q: What is wind chill?
A: Wind chill is the “measure of how cold the air feels on your skin.”
Q: How is wind chill calculated?
A: Wind chill is calculated using a formula that takes into account the air temperature, wind speed, and heat transfer theory and skin tissue resistance.
Q: What is the formula for wind chill?
A: The formula is: 35.74 + 0.6215T – 35.75 (V^0.16) + 0.4275T(V^0.16) = Wind chill
Q: How does wind chill affect the body?
A: The wind makes it FEEL much colder, as it draws heat from the body and reduces the body’s natural insulation.
Q: Is wind chill the same as the actual temperature?
A: No, wind chill is the “feels-like” temperature, which can be different from the actual air temperature.
