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
The agency said that heat index values could reach 110F in Louisiana and South Carolina; 109F in Georgia and Arkansas; 108F in Maryland and Alabama; 104F in Kentucky; and 103F in New York.
—Matthew Robinson, MSNBC Newsweek, 25 June 2025
Temperatures soared past 95 degrees in many parts of Pennsylvania, with heat index values above 100 degrees expected in cities such as Philadelphia, Lancaster and Pittsburgh.
—Bill Chappell, NPR, 24 June 2025
Temperatures are expected to be in the mid-90s in the metro, with heat index values as high as 103 degrees.
—Robert A. Cronkleton, Kansas City Star, 23 June 2025
Almost 59 million Americans were under an extreme heat warning Saturday, Hurley said, as the high temperatures combined with humidity pushed an above-average heat index for the Northern Plains and the Midwest.
—Arkansas Online, 22 June 2025
If someone is outside and exposed to the direct sun, the actual heat index can be as much as 15 F higher than the heat index chart indicates.
—Brian Bossak, The Conversation, 19 June 2025
Peak heat indices range between 100 and 105 degrees.
—Garfield Hylton, The Orlando Sentinel, 19 June 2025
Other parts of the state, including Raleigh and Fayetteville, are also expected to see heat index temperatures in the triple digits, according to WRAL.
—Jeff A. Chamer, Charlotte Observer, 19 June 2025
With a temperature pushing 90 and a heat index of 100, the weather proved a formidable foe.
—Howard Cohen, Miami Herald, 14 June 2025
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Matthew Robinson, MSNBC Newsweek, 25 June 2025
Temperatures soared past 95 degrees in many parts of Pennsylvania, with heat index values above 100 degrees expected in cities such as Philadelphia, Lancaster and Pittsburgh.
—Bill Chappell, NPR, 24 June 2025
Temperatures are expected to be in the mid-90s in the metro, with heat index values as high as 103 degrees.
—Robert A. Cronkleton, Kansas City Star, 23 June 2025
Almost 59 million Americans were under an extreme heat warning Saturday, Hurley said, as the high temperatures combined with humidity pushed an above-average heat index for the Northern Plains and the Midwest.
—Arkansas Online, 22 June 2025
If someone is outside and exposed to the direct sun, the actual heat index can be as much as 15 F higher than the heat index chart indicates.
—Brian Bossak, The Conversation, 19 June 2025
Peak heat indices range between 100 and 105 degrees.
—Garfield Hylton, The Orlando Sentinel, 19 June 2025
Other parts of the state, including Raleigh and Fayetteville, are also expected to see heat index temperatures in the triple digits, according to WRAL.
—Jeff A. Chamer, Charlotte Observer, 19 June 2025
With a temperature pushing 90 and a heat index of 100, the weather proved a formidable foe.
—Howard Cohen, Miami Herald, 14 June 2025
Cite this Entry
“Heat index.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/heat%20index. Accessed 4 Jul. 2025.
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