heat index
noun
plural heat indexes or heat indices
: a value that indicates what the ambient temperature feels like to the human body and that is derived from a calculation using air temperature and relative humidity
The most likely chances for a heat advisory are Thursday and Friday, when the heat index could approach at least 100 degrees, according to National Weather Service meteorologists …—
Julie E. Greene
Julie E. GreeneThe heat index is defined as a function of temperature and relative humidity. The combination of the two results in an apparent temperature that gives an idea of what the hot and humid air feels like to the average person.—Neil MacFarquhar
Neil MacFarquharExamples of heat index in a Sentence
Recent Examples on the Web
With heat index values expected to climb into the triple digits by the weekend, people across the metro should prepare for a return to summer conditions.
—Kansas City Star, 12 Aug. 2025
Detroit: 91 degrees; heat index values up to 93 degrees.
—Sarah Moore, Freep.com, 9 Aug. 2025
The National Weather Service has issued urgent warnings for large swathes of Arkansas, Louisiana, Mississippi, Texas, Tennessee and Arizona, where heat index values are forecast to soar as high as 120 F in some areas.
—Martha McHardy, MSNBC Newsweek, 31 July 2025
The National Weather Service predicted temperatures in Savannah would reach 97 F (36 C) Tuesday, with heat index values — what the temperature feels like — approaching a broiling 110 F (43 C).
—Sasha Rogelberg, Fortune, 30 July 2025
Much of Tennessee is under a heat dome that has brought triple-digit temperatures to communities and an even higher heat index.
—Joyce Orlando, Nashville Tennessean, 29 July 2025
This will minimize any concerns about higher heat index readings for the afternoon.
—Mary Wasson, Austin American Statesman, 30 July 2025
Areas with extreme heat have temperatures ranging from 95 to 100 degrees, with a heat index ranging from 112 to 115 degrees.
—Garfield Hylton, The Orlando Sentinel, 29 July 2025
Temperatures during the week are expected to be in the high 90s with a heat index upwards of 114 degrees.
—Joyce Orlando, The Tennessean, 29 July 2025
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Kansas City Star, 12 Aug. 2025
Detroit: 91 degrees; heat index values up to 93 degrees.
—Sarah Moore, Freep.com, 9 Aug. 2025
The National Weather Service has issued urgent warnings for large swathes of Arkansas, Louisiana, Mississippi, Texas, Tennessee and Arizona, where heat index values are forecast to soar as high as 120 F in some areas.
—Martha McHardy, MSNBC Newsweek, 31 July 2025
The National Weather Service predicted temperatures in Savannah would reach 97 F (36 C) Tuesday, with heat index values — what the temperature feels like — approaching a broiling 110 F (43 C).
—Sasha Rogelberg, Fortune, 30 July 2025
Much of Tennessee is under a heat dome that has brought triple-digit temperatures to communities and an even higher heat index.
—Joyce Orlando, Nashville Tennessean, 29 July 2025
This will minimize any concerns about higher heat index readings for the afternoon.
—Mary Wasson, Austin American Statesman, 30 July 2025
Areas with extreme heat have temperatures ranging from 95 to 100 degrees, with a heat index ranging from 112 to 115 degrees.
—Garfield Hylton, The Orlando Sentinel, 29 July 2025
Temperatures during the week are expected to be in the high 90s with a heat index upwards of 114 degrees.
—Joyce Orlando, The Tennessean, 29 July 2025
Cite this Entry
“Heat index.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/heat%20index. Accessed 22 Aug. 2025.
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