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.

An 'extreme heat watch' is in effect as the heat index is expected to skyrocket. Here's timing, updated heat index values, more.

An 'extreme heat watch' is in effect as the heat index is expected to skyrocket. Here's timing, updated heat index values, more.

Heat index chart measuring the air temperatures and relative humidity to produce an apparent temperature.

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.

Extreme danger: When the heat index is 125 degrees or higher, heat stroke is likely. Here's a chart to help you find out what the heat index is. You can also use this heat index calculator. Certain ...

Extreme danger: When the heat index is 125 degrees or higher, heat stroke is likely. Heat index calculator Here's a chart to help you find out what the heat index is.

The heat index chart that the National Weather Service uses measures what temperatures will feel like in the shade. In direct sunlight, the agency warns heat index values can increase by up to 15 ...