How Is Wind Chill Calculated

Calculate Wind Chill

Enter the air temperature and wind speed to find out how cold it really feels.

Wind Chill Table

Wind Speed (mph)	Wind Chill (°F) at Current Temp (20°F)

Wind chill values for various wind speeds at the entered air temperature.

What is Wind Chill?

Wind chill, often referred to as the “feels like” temperature, is a measure of the rate of heat loss from the human body resulting from the combined effect of low air temperature and wind speed. It’s not the actual temperature of the air, but rather how cold human skin perceives it to be due to the wind carrying heat away from the body more rapidly. When the wind blows across exposed skin, it disrupts the insulating layer of warm air that normally surrounds us, leading to faster cooling. Understanding how is wind chill calculated helps us prepare for cold weather conditions.

The concept is primarily used in cold climates to communicate the increased risk of cold-related injuries like frostbite and hypothermia. The lower the wind chill temperature, the faster exposed skin will cool, and the shorter the time until frostbite can occur. It’s important for anyone spending time outdoors in cold, windy conditions, including hikers, skiers, outdoor workers, and the general public, to be aware of the wind chill.

A common misconception is that wind chill affects inanimate objects, causing them to cool below the actual air temperature. This is incorrect. Objects will cool down to the air temperature faster in windy conditions, but they will not get colder than the air temperature itself, regardless of the wind chill. The wind chill index is specifically for estimating the effect on exposed human or animal skin.

Wind Chill Formula and Mathematical Explanation

The most commonly used formula for how is wind chill calculated in the United States and Canada was implemented in 2001. It’s based on heat loss from the exposed face of a person walking at 3 mph directly into the wind, combined with modern heat transfer theory.

The formula is:

Wind Chill (°F) = 35.74 + 0.6215*T – 35.75*(V^0.16) + 0.4275*T*(V^0.16)

Where:

• T = Air Temperature in degrees Fahrenheit (°F)
• V = Wind Speed in miles per hour (mph)

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

Step-by-step breakdown:

1. Calculate V^0.16: Raise the wind speed in mph to the power of 0.16.
2. Calculate the terms:
   • 0.6215 * T
   • -35.75 * (V^0.16)
   • 0.4275 * T * (V^0.16)
3. Sum the constant (35.74) and the calculated terms to get the wind chill temperature.

Variables Table

Variable	Meaning	Unit	Typical Range (for formula use)
T	Air Temperature	°F	-50°F to 50°F
V	Wind Speed	mph	3 mph and above
Wind Chill	Calculated “feels like” temperature	°F	Usually lower than T

If the wind speed is below 3 mph, the wind chill is generally considered to be the same as the air temperature, as the formula’s accuracy decreases at very low wind speeds.

Practical Examples (Real-World Use Cases)

Example 1: A Cold, Breezy Day

Imagine the air temperature is 20°F and the wind is blowing at 15 mph.

• T = 20°F
• V = 15 mph

Using the formula: Wind Chill = 35.74 + 0.6215*(20) – 35.75*(15^0.16) + 0.4275*(20)*(15^0.16)

15^0.16 ≈ 1.696

Wind Chill ≈ 35.74 + 12.43 – 35.75*(1.696) + 0.4275*(20)*(1.696)

Wind Chill ≈ 35.74 + 12.43 – 60.62 + 14.50 ≈ 2.05 °F

So, although the air temperature is 20°F, it feels like approximately 2°F due to the wind. This significantly increases the risk of frostbite compared to 20°F with no wind.

Example 2: Very Cold and Windy

Consider a very cold day with an air temperature of 0°F and a strong wind of 30 mph.

• T = 0°F
• V = 30 mph

Using the formula: Wind Chill = 35.74 + 0.6215*(0) – 35.75*(30^0.16) + 0.4275*(0)*(30^0.16)

30^0.16 ≈ 1.959

Wind Chill ≈ 35.74 + 0 – 35.75*(1.959) + 0

Wind Chill ≈ 35.74 – 70.04 ≈ -34.3 °F

In this scenario, the wind chill is about -34°F, indicating extremely dangerous conditions where exposed skin can freeze very quickly.

How to Use This Wind Chill Calculator

Our calculator makes it easy to understand how is wind chill calculated for your specific conditions:

1. Enter Air Temperature: Input the current ambient air temperature in degrees Fahrenheit (°F) into the “Air Temperature (°F)” field.
2. Enter Wind Speed: Input the sustained wind speed in miles per hour (mph) into the “Wind Speed (mph)” field. The formula works best for wind speeds of 3 mph or higher. If you enter a value below 3, the calculator will likely show the wind chill as equal to the air temperature.
3. View Results: The calculator will instantly display the calculated Wind Chill temperature in the “Results” section, highlighted as the primary result. You will also see the intermediate terms from the formula.
4. Check Chart and Table: The chart and table below the calculator will update to show wind chill values for different wind speeds at the temperature you entered, giving you a broader understanding.
5. Reset or Copy: Use the “Reset” button to return to default values or “Copy Results” to copy the main findings.

When reading the results, remember the wind chill is an estimate of how cold it feels on exposed skin. Use this information to dress appropriately in layers, cover exposed skin, and limit time outdoors in very low wind chill conditions to prevent frostbite and hypothermia. See our guide on cold weather safety for more tips.

Key Factors That Affect Wind Chill Results

Several factors influence the wind chill value and the body’s reaction to cold:

1. Air Temperature: This is the primary input. The colder the air, the lower the starting point for heat loss, and thus the lower the wind chill for a given wind speed.
2. Wind Speed: The other direct input into the formula. Higher wind speeds dramatically increase the rate of heat loss from the body, resulting in a lower wind chill temperature. This is the core of how is wind chill calculated.
3. Exposure: The wind chill index applies to exposed skin. Covering skin with clothing, hats, gloves, and face masks reduces the wind’s effect and the rate of heat loss.
4. Humidity: While not directly in the standard wind chill formula, very high or very low humidity can subtly affect how cold it feels and the rate of heat loss, though its effect is much less significant than temperature and wind in cold conditions compared to its effect in hot conditions (heat index).
5. Solar Radiation (Sunlight): Bright sunshine can make it feel warmer than the air temperature or wind chill suggests because the sun’s radiation adds heat to the body. The wind chill calculation assumes no warming effect from the sun (e.g., it’s more accurate at night or on cloudy days).
6. Individual Factors: A person’s metabolism, body fat percentage, clothing, and activity level also influence how they perceive cold and lose heat. The wind chill is a standardized value.
7. Altitude: Higher altitudes often have lower temperatures and potentially higher wind speeds, indirectly affecting wind chill. Air is also less dense at higher altitudes, which can slightly alter heat loss rates. Learn more about temperature scales and their variations.

Frequently Asked Questions (FAQ)

Q1: What is the wind chill formula?

A1: The formula used in the US and Canada is: Wind Chill (°F) = 35.74 + 0.6215*T – 35.75*(V^0.16) + 0.4275*T*(V^0.16), where T is air temperature in °F and V is wind speed in mph (≥3 mph).

Q2: Can wind chill be warmer than the actual air temperature?

A2: No, wind chill is either equal to the air temperature (at very low or no wind) or colder than the air temperature because the wind enhances heat loss.

Q3: Does wind chill affect my car or house?

A3: Wind chill does not cause inanimate objects like cars or houses to cool below the actual air temperature. However, the wind will cause them to cool *down to* the air temperature faster than they would in calm conditions.

Q4: At what wind speed does the wind chill formula apply?

A4: The standard formula is most accurate for wind speeds of 3 mph or greater. Below 3 mph, the wind chill is often reported as being equal to the air temperature.

Q5: How do I convert wind chill from Fahrenheit to Celsius?

A5: Once you calculate the wind chill in °F, you can convert it to °C using the formula: °C = (°F – 32) * 5/9. Our temperature converter can help.

Q6: Is there a wind chill chart I can refer to?

A6: Yes, many weather services provide wind chill charts that show the wind chill temperature for various combinations of air temperature and wind speed. Our calculator also generates a dynamic table.

Q7: What is frostbite and how is it related to wind chill?

A7: Frostbite is an injury caused by freezing of the skin and underlying tissues. Lower wind chill values mean a faster rate of heat loss, which increases the risk of frostbite and reduces the time it takes for it to occur on exposed skin. For more information, check winter weather preparedness.

Q8: Is the wind chill the same as the “feels like” temperature?

A8: Yes, “wind chill” is the term used in cold conditions to describe the “feels like” temperature, which combines air temperature and wind speed. In warm conditions, the “feels like” temperature is often described by the Heat Index, which combines air temperature and humidity. You can use our heat index calculator for that.