The heat index is a complicated calculation that factors humidity into the air temperature, giving us a more representative number of how it feels outside when the humidity is high. It looks like ...

The heat index is a measure of how hot it really feels on your body when relative humidity is factored in with the actual air temperature.

Residents can use the NWS Heat Index Calculator to calculate what the heat index is locally. In addition, there is the Heat Index Chart with a wider range of temperatures and humidity percentages.

Residents can use the NWS Heat Index Calculator to calculate what the heat index is locally. In addition, there is the Heat Index Chart with a wider range of temperatures and humidity percentages.

The heat index is a formula developed by the U.S. National Weather Service based on Robert G. Steadman’s 1979 paper “ The Assessment of Sultriness.” Prior to that, it didn’t exist.

With a heat wave causing excessive heat warnings in Delaware, you'll hear a lot about the heat index this week. What to know and how to stay cool.