Heat Index Calculator
Calculate the heat index and what the temperature feels like with humidity factored in using the official NOAA formula.
Top Cities
Top cities where Heat Index calculations are checked
Top Countries
Top countries where Heat Index calculations are checked
Calculation Statistics
See how many Heat Index calculations have been made over time
Understanding Heat Index
What is Heat Index?
Heat index, also known as apparent temperature, is what the temperature feels like to the human body when relative humidity is combined with the air temperature.
The NOAA Formula
We use the official NOAA Rothfusz regression equation, which provides accurate heat index values for temperatures above 80°F with various humidity levels.
Heat Risk Levels
80-90°F: Caution
91-103°F: Extreme Caution
104-125°F: Danger
126°F+: Extreme Danger
Safety Tips
Stay hydrated, wear light clothing, limit outdoor activities during peak heat, seek air-conditioned spaces, and watch for signs of heat exhaustion or heat stroke.
Heat Index Calculator Guides & Articles
Staying Safe in Extreme Heat
Learn essential tips for protecting yourself and your family when heat index values reach dangerous levels.
Recognizing Heat Exhaustion
Know the warning signs of heat-related illnesses and what to do if you or someone else is affected.
Humidity and Heat: A Dangerous Combo
Understand why humidity makes hot temperatures feel even more oppressive and dangerous.
Frequently Asked Questions
The heat index is a measure of how hot it really feels when humidity is factored in with the actual air temperature. It's sometimes called the "apparent temperature."
A heat index of 103°F or higher is considered dangerous. At this level, heat stroke becomes possible with prolonged exposure and/or physical activity.
High humidity prevents sweat from evaporating effectively. Since evaporation is how our bodies cool down, high humidity makes it harder to regulate body temperature.
Elderly individuals, young children, those with chronic illnesses, outdoor workers, and athletes are at higher risk of heat-related illness.