How Is Wind Chill Calculated

This calculator determines the wind chill temperature based on the air temperature and wind speed, explaining how is wind chill calculated using the standard formula.

Calculate Wind Chill

Wind Chill Chart (°F) – How wind chill varies with temperature and wind speed

Temp (°F) / Wind (mph)	5	10	15	20	25	30

What is Wind Chill?

Wind chill, more formally known as the Wind Chill Temperature (WCT) index, is a measure of how cold it really feels outside when the wind is factored in with the actual air temperature. It’s not the actual temperature of the air, but rather an expression of the rate of heat loss from exposed skin caused by the combined effects of wind and cold. The question of how is wind chill calculated is answered by a specific formula developed to estimate this cooling effect.

Essentially, when the wind blows across exposed skin, it carries away heat from the body’s surface more rapidly. The stronger the wind, the faster the heat loss, and the colder it feels. The wind chill index gives a number that approximates the equivalent temperature in calm air that would produce the same rate of heat loss.

This index is primarily used in cold climates during winter to alert people to the dangers of frostbite and hypothermia. It applies to people and animals with exposed skin or fur, but not to inanimate objects like cars or pipes, which will only cool down to the actual air temperature, though they might do so faster with wind.

Who should use it?

Anyone spending time outdoors in cold, windy conditions should be aware of the wind chill. This includes:

• People working outdoors (construction, emergency services).
• Those participating in winter sports (skiing, snowboarding, ice skating).
• Commuters waiting for public transport.
• Children playing outside.
• Pet owners taking their animals for walks.

Understanding how is wind chill calculated and its implications helps in dressing appropriately and taking necessary precautions.

Common Misconceptions

A common misconception is that the wind chill is the actual temperature the air or objects will reach. This is incorrect. An object will not cool below the actual air temperature, no matter how strong the wind. Wind chill only describes the rate of heat loss from a warm body and the perceived coldness on exposed skin.

Wind Chill Formula and Mathematical Explanation

The current formula for calculating wind chill temperature (WCT) used in North America (by the National Weather Service in the US and the Meteorological Service of Canada) was implemented in 2001. It is based on a model of heat loss from the exposed face. The formula for how is wind chill calculated is:

WCT (°F) = 35.74 + 0.6215T – 35.75(V^0.16) + 0.4275T(V^0.16)

Where:

• WCT is the Wind Chill Temperature in degrees Fahrenheit (°F).
• T is the air temperature in degrees Fahrenheit (°F).
• V is the wind speed in miles per hour (mph), measured at the standard height of 10 meters (33 feet).

This formula is valid for air temperatures at or below 50 °F and wind speeds at or above 3 mph.

Variables Table

Variable	Meaning	Unit	Typical Valid Range
T	Air Temperature	°F	≤ 50 °F
V	Wind Speed	mph	≥ 3 mph
WCT	Wind Chill Temperature	°F	Calculated value

The term V^0.16 represents the effect of wind speed raised to the power of 0.16, which was determined through experiments and modeling to best fit the heat loss data from human skin.

Practical Examples (Real-World Use Cases)

Example 1: A Cold and Windy Day

Let’s say the air temperature is 10°F and the wind is blowing at 20 mph.

• T = 10 °F
• V = 20 mph

Plugging these into the formula:
WCT = 35.74 + 0.6215(10) – 35.75(20^0.16) + 0.4275(10)(20^0.16)

20^0.16 ≈ 1.812

WCT ≈ 35.74 + 6.215 – 35.75(1.812) + 4.275(1.812)

WCT ≈ 35.74 + 6.215 – 64.785 + 7.746

WCT ≈ -15.08 °F

So, with an air temperature of 10°F and a 20 mph wind, it feels like -15°F on exposed skin. This is a significant difference and highlights the importance of understanding how is wind chill calculated for safety.

Example 2: A Milder but Breezy Day

If the air temperature is 35°F and the wind speed is 10 mph:

• T = 35 °F
• V = 10 mph

WCT = 35.74 + 0.6215(35) – 35.75(10^0.16) + 0.4275(35)(10^0.16)

10^0.16 ≈ 1.445

WCT ≈ 35.74 + 21.7525 – 35.75(1.445) + 14.9625(1.445)

WCT ≈ 35.74 + 21.7525 – 51.66875 + 21.6208

WCT ≈ 27.45 °F

Even at 35°F, a 10 mph wind makes it feel like about 27°F. See our frostbite safety guide for more info.

How to Use This Wind Chill Calculator

1. Enter Air Temperature: Input the current or forecast air temperature in degrees Fahrenheit (°F) into the “Air Temperature (T)” field. The formula is valid for 50°F or below.
2. Enter Wind Speed: Input the sustained wind speed in miles per hour (mph) into the “Wind Speed (V)” field. The formula is valid for 3 mph or above.
3. View Results: The calculator automatically updates and shows the calculated Wind Chill Temperature in °F. It also displays a table and chart for context.
4. Interpret Results: The Wind Chill Temperature is the “feels like” temperature on exposed skin. Use this value to assess the risk of cold-related injuries like frostbite and hypothermia and dress accordingly. For more on cold weather, see our winter safety guide.
5. Reset: Click the “Reset” button to return to default values.
6. Copy: Click “Copy Results” to copy the inputs and results.

The table and chart help visualize how is wind chill calculated and how it changes with different conditions.

Key Factors That Affect Wind Chill Results

Several factors influence the wind chill and its effect on you:

1. Air Temperature: The lower the air temperature, the lower the wind chill, and the faster heat is lost.
2. Wind Speed: Higher wind speeds increase the rate of heat loss from the skin, resulting in a lower wind chill temperature. This is central to how is wind chill calculated.
3. Exposure: The amount of exposed skin significantly affects heat loss. Covering skin reduces the impact of wind chill.
4. Clothing: Wearing layers of clothing, especially wind-resistant outer layers, traps air and insulates the body, reducing heat loss.
5. Physical Activity: Being active generates body heat, which can offset some of the heat loss due to wind chill, but sweat can increase heat loss if it gets wet.
6. Sunlight: Bright sunshine can make it feel slightly warmer than the wind chill temperature suggests, although the formula doesn’t account for solar radiation. Check our understanding wind chill page for more details.
7. Humidity: While not directly in the standard wind chill formula, high humidity in very cold air can make it feel even colder as moisture conducts heat away from the body more efficiently than dry air, although this effect is more pronounced with the heat index in warm weather. You might also be interested in our heat index calculator.

Frequently Asked Questions (FAQ)

What is wind chill?

Wind chill is an index that indicates how cold it feels on exposed human skin due to the combined effect of air temperature and wind speed.

How is wind chill calculated?

Wind chill is calculated using a formula that takes air temperature (T in °F) and wind speed (V in mph) as inputs: WCT = 35.74 + 0.6215T – 35.75(V^0.16) + 0.4275T(V^0.16).

Does wind chill affect inanimate objects?

No, wind chill only describes the rate of heat loss from warm-blooded animals or humans. Inanimate objects will cool to the air temperature, although faster with wind, but not below it.

At what temperature and wind speed is the wind chill formula valid?

The standard formula is valid for air temperatures of 50°F or lower and wind speeds of 3 mph or higher.

What is frostbite and when can it occur?

Frostbite is an injury caused by freezing of the skin and underlying tissues. The risk of frostbite increases significantly at lower wind chill values. For example, at a wind chill of -20°F, frostbite can occur in about 30 minutes on exposed skin. Our frostbite time guide has more.

How should I dress based on wind chill?

Dress in layers, with a wind-resistant outer layer. Cover as much exposed skin as possible, including hands, face, and ears.

Is the wind chill temperature the same as the actual air temperature?

No, the wind chill temperature is usually lower than the air temperature when it’s cold and windy. It represents the “feels like” temperature for exposed skin.

Can I get frostbite even if the air temperature is above freezing?

It’s very unlikely to get frostbite if the air temperature is above 32°F, even with high winds, as the skin won’t freeze. However, hypothermia is still a risk with prolonged exposure to cold and wet conditions even above freezing. Learn about temperature scales.