Calculate the heat index (feels-like temperature) based on temperature and humidity. Get heat safety warnings and health recommendations. Pure client-side.
The Heat Index, also known as the "feels-like" temperature, is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature. The human body cools itself by sweating, but high humidity reduces the effectiveness of this cooling mechanism. This calculator uses the National Weather Service (NWS) heat index formula to provide accurate results and heat safety warnings. All calculations happen in your browser — no data is sent to any server.