Wind Chill and Feels-Like Temperature Explained
The temperature shown on a thermometer tells you about the air, but not how it feels on your skin. Wind and humidity both change how quickly your body loses or retains heat, creating a perceived temperature that differs from the measured one. This calculator uses two internationally recognized formulas to determine the real feels-like temperature based on your conditions.
Wind Chill Index
Wind accelerates heat loss from exposed skin through convection. The Wind Chill Index quantifies this effect using the formula jointly adopted by the US National Weather Service and Environment Canada in 2001: Wind Chill = 13.12 + 0.6215T − 11.37V^0.16 + 0.3965T × V^0.16, where T is air temperature in °C and V is wind speed in km/h. This formula applies when temperature is 10°C or below and wind speed is at least 4.8 km/h.
As a practical example: at -10°C with a 30 km/h wind, the feels-like temperature drops to about -20°C — a 10-degree difference that significantly changes frostbite risk timelines.
Heat Index
In hot weather, high humidity reduces the evaporation of sweat from your skin, which is the body's primary cooling mechanism. The Heat Index (NOAA Rothfusz regression equation) applies when temperature is 27°C or above and relative humidity is 40% or higher. At 35°C with 80% humidity, the feels-like temperature can exceed 40°C — well into dangerous heat territory.
Safety Thresholds
At a feels-like temperature of -15°C, frostbite can occur within 30 minutes on exposed skin. At -25°C that window shrinks to 10–15 minutes. On the hot side, a heat index above 40°C carries a high risk of heat cramps and heat exhaustion, while above 54°C heatstroke becomes likely without immediate cooling.
Frequently Asked Questions
- Does sunshine affect the feels-like temperature?
- These formulas are based on shade. Direct sunlight can add 6–11°C to the Heat Index. For outdoor activities in full sun, treat the calculated result as a conservative baseline.
- Why doesn't wind chill apply above 10°C?
- At warmer temperatures, the cooling effect of wind is not significant enough to lower perceived temperature meaningfully below the air temperature. The formula is validated only for cold conditions.