Heat Index Calculator
Calculate what the temperature really feels like based on relative humidity. Essential for outdoor safety and heat stroke prevention.
Valid range typically > 80°F
Standard is ~40-60%.
What is the Heat Index?
The Heat Index, sometimes referred to as the "apparent temperature," is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature.
When humidity is high, sweat cannot evaporate as easily from the skin. Evaporation is the body's primary way of cooling itself. If sweat cannot evaporate, the body retains heat, making it feel hotter than the thermometer reads.
Safety Tips for High Heat Index
- Stay Hydrated: Drink plenty of water, even if you don't feel thirsty. Avoid alcohol and caffeine.
- Limit Outdoor Activity: Try to schedule strenuous activities for early morning or late evening when it is cooler.
- Seek Shade & AC: Air conditioning is the best protection against heat-related illness. If you don't have AC, spend time in public facilities like libraries or malls.
- Wear Proper Clothing: Choose lightweight, light-colored, and loose-fitting clothes.
Heat Disorders
Prolonged exposure to extreme heat can lead to:
- Heat Cramps: Muscle pains or spasms, usually in the abdomen, arms, or legs.
- Heat Exhaustion: Heavy sweating, paleness, muscle cramps, tiredness, weakness, dizziness, headache, nausea or vomiting, and fainting.
- Heat Stroke: Extremely high body temperature (above 103°F), red/hot/dry skin (no sweating), rapid pulse, throbbing headache, dizziness, nausea, confusion, and unconsciousness. This is a medical emergency. Call 911 immediately.
? Frequently Asked Questions
High humidity prevents sweat from evaporating efficiently. This evaporation process is what cools your body down. Without it, you retain body heat, creating the sensation of a much higher temperature.
Similar, but not identical. Heat Index is a specific scientific formula based on shade conditions. 'RealFeel' is a proprietary algorithm by AccuWeather that also factors in wind, cloud cover, and sun intensity.
No. The standard Heat Index formula assumes light wind in the shade. However, strong hot winds can actually heat the body further (like a convection oven), while cool breezes might help evaporation.