Wind Chill & Heat Index Calculator
See how cold or hot it really feels using official National Weather Service formulas. Check wind chill danger, frostbite risk, heat index, and heat illness categories in one tool.
Wind chill estimates how cold it feels on exposed skin when air temperature and wind combine.
Feels Like
21.6°F
-5.8°C
Danger Level
Caution
Frostbite is unlikely, but prolonged exposure can still be uncomfortable.
Formula note
Calculated with the official NWS wind chill formula.
How to Use
- Choose the Wind Chill or Heat Index tab.
- Enter the air temperature and pick Fahrenheit or Celsius.
- For wind chill, enter wind speed in mph or km/h. For heat index, enter relative humidity.
- Review the feels-like temperature, danger category, and the safety guidance shown below the result.
Frequently Asked Questions
When is the wind chill formula accurate?
The official NWS wind chill formula is intended for temperatures at or below 50°F and wind speeds above 3 mph. Outside that range, this calculator shows the air temperature and explains that the formula is not officially applicable.
What is heat index?
Heat index is the apparent temperature your body experiences when heat and humidity are combined. Higher humidity slows sweat evaporation, making the air feel hotter than the thermometer reading.
Why can wind chill be lower than the actual temperature?
Moving air removes heat from exposed skin more quickly than still air. That extra heat loss makes conditions feel colder and increases the risk of cold-related injuries like frostbite.
What heat index level is dangerous?
According to standard NWS guidance, heat index values from 90°F to 103°F are extreme caution, 103°F to 124°F are danger, and 125°F or higher are extreme danger. Risk rises further with sun exposure, exertion, age, and dehydration.