GlenCalc

Heat index calculator

Humid air slows the cooling effect of sweat, so it feels hotter than it is. Values are for shade and light wind; full sun can add up to 15 °F.

Your answer

Heat index104.7 °FDanger

Worked out in your browser. Nothing you type is sent to a server.

How we worked it out

Updated as you change the numbers.

  1. Below about 80 °F a simple formula is used; above it, the Rothfusz regression with the NWS adjustments for very dry and very humid air.

Method and assumptions

This follows the National Weather Service’s method: Steadman’s simple formula for mild conditions and the Rothfusz regression otherwise, with its low- and high-humidity adjustments. The risk categories are the NWS’s.

Questions

What is the heat index at 92 °F and 60% humidity?

About 105 °F: danger level.

Sources

Method and figures checked on . Every worked answer on this page is covered by an automated test. Found a mistake? Tell us.

Embed this calculator on your site

Free to use. Paste this where you want the calculator; it runs in your visitors’ browsers, sets no cookies and sends nothing to us.

Related calculators