What is wind chill and how is it calculated?

Wind chill is the perceived decrease in air temperature felt by the body on exposed skin due to the flow of air. It's calculated using the air temperature and wind speed. The formula, developed by the U.S. National Weather Service, accounts for how wind strips away the thin layer of warm air at the surface of your skin, making you feel colder.

How do I calculate heat index from temperature and humidity?

The heat index, or 'feels like' temperature, combines air temperature and relative humidity to determine how hot it really feels. High humidity reduces the evaporation rate of sweat, which is the body's primary cooling mechanism. Our calculator uses a complex multiple regression equation developed by the National Weather Service, which involves temperature, humidity, and their interactions.

What is dew point and why does it matter?

The dew point is the temperature to which air must be cooled to become saturated with water vapor, leading to the formation of dew. It's a more absolute measure of how much moisture is in the air than relative humidity. A high dew point (e.g., above 65°F or 18°C) indicates humid, uncomfortable conditions, while a low dew point feels dry and comfortable.

Can I use this calculator for both Celsius and Fahrenheit?

Yes. The calculator is designed for convenience and supports both Metric (°C, kph) and Imperial (°F, mph) units. You can easily toggle between the unit systems, and the calculations will be automatically converted and performed using the appropriate formula.

How accurate are these weather calculations?

The calculations are highly accurate as they are based on standardized, peer-reviewed formulas used by meteorological organizations like the National Weather Service (NWS). However, they are models and assume certain conditions (e.g., a person of average height and weight, walking in a shaded area for heat index). Local factors can influence the real-world 'feels like' temperature.

Are these calculations suitable for outdoor safety planning?

Absolutely. Wind chill and heat index are crucial for outdoor safety. Extreme wind chill can lead to frostbite and hypothermia, while a high heat index increases the risk of heat exhaustion and heatstroke. Use this calculator to assess conditions and take necessary precautions, like dressing appropriately or limiting exposure during extreme weather.

Wind Chill, Heat Index & Dew Point Calculator — Weather Temperature Effects

🌡️ Weather Effects Calculator

Calculate Wind Chill, Heat Index, and Dew Point

Air Temperature

Wind Speed

Relative Humidity

What Are Wind Chill, Heat Index, and Dew Point?

When you check the weather, you often see more than just the temperature. Terms like "feels like," "wind chill," and "heat index" are used to describe how weather conditions actually feel on the human body. These perceived temperatures are often more important for health and safety than the air temperature alone.

Wind Chill: This index describes the rate of heat loss on the human body resulting from the combined effect of low temperature and wind. As wind speed increases, it draws heat from the body, driving down skin temperature and eventually the internal body temperature. This is why a calm, cold day feels much more manageable than a windy, cold day of the same temperature.
Heat Index: This is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature. Your body cools itself by sweating, which evaporates and carries heat away. When humidity is high, sweat doesn't evaporate as efficiently, so your body feels hotter than the air temperature.
Dew Point: The dew point temperature is the point at which the air becomes saturated with water vapor and dew begins to form. It's a more direct measure of the amount of moisture in the air than relative humidity. When the dew point is high (e.g., above 65°F / 18°C), the air feels muggy and oppressive, making it difficult for the body to cool itself.

How We Calculate Perceived Temperature

This calculator uses scientifically-backed formulas developed by meteorological agencies to provide accurate estimations. We don't just guess—we use the same math that weather forecasters rely on.

For Wind Chill, we use the National Weather Service (NWS) formula, which was updated in 2001 based on human trials and advanced heat transfer theory. The formula is: WC = 35.74 + 0.6215T - 35.75(V^0.16) + 0.4275T(V^0.16), where T is the air temperature in °F and V is the wind speed in mph.

For Heat Index, we implement the Steadman formula, refined by the NWS through a multiple regression analysis. It's a complex polynomial equation that accounts for the non-linear relationship between temperature, humidity, and perceived heat.

For Dew Point, we use the well-established Magnus formula, a highly accurate approximation for calculating the dew point from temperature and relative humidity. It involves logarithmic functions to model the relationship between water vapor pressure and temperature.

Why These Weather Calculations Matter for Outdoor Safety

Understanding perceived temperature is critical for anyone who spends time outdoors, whether for work, recreation, or athletics. Ignoring these values can have serious health consequences.

Cold Weather Safety: A low wind chill significantly increases the risk of cold-related injuries like frostbite and hypothermia. Exposed skin can freeze in a matter of minutes in extreme wind chill conditions. Using this calculator helps you dress appropriately in layers and know when it's safer to stay indoors.

Hot Weather Safety: A high heat index indicates a greater risk for heat-related illnesses such as heat cramps, heat exhaustion, and potentially fatal heatstroke. When the heat index is high, it's crucial to stay hydrated, seek shade, limit strenuous activity, and be aware of the symptoms of heat illness, especially for vulnerable populations like children and the elderly.

Frequently Asked Questions

Q: What's the difference between dew point and humidity?
A: Relative humidity tells you how saturated the air is relative to its maximum capacity at a given temperature. Dew point is an absolute measure of how much moisture is in the air. A 70°F dew point always feels the same (muggy), whereas 70% humidity can feel very different at 30°F versus 90°F.

Q: Is there a wind chill effect when it's warm?
A: The official wind chill formula is only defined for temperatures at or below 50°F (10°C) and wind speeds above 3 mph. While wind can have a cooling effect on a hot day (which is why fans work), it is not referred to as "wind chill" and is instead a factor in the heat index calculation.

Q: Can I get frostbite even if the temperature is above freezing?
A: No. Frostbite requires temperatures to be at or below the freezing point of water, 32°F (0°C). However, a strong wind chill can make it feel much colder and can rapidly accelerate the onset of hypothermia, which is a dangerous drop in core body temperature.

Disclaimer: This tool provides estimates for informational and planning purposes only. It is not a substitute for official weather advisories from a qualified meteorological service. For safety-critical decisions, please consult official sources like the National Weather Service or your local weather authority.