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
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
Heat advisories issued for much of the South National Weather Service heat advisories also have been issued across much of the South, with heat index values up to 112 expected across portions of Mississippi, Alabama and Florida.
—John Bacon, USA Today, 28 July 2025
Parts of Mississippi and Louisiana are on alert for heat indices up to 120 degrees.
—Youri Benadjaoud, ABC News, 28 July 2025
High temperatures in the upper 90s to low 100s are expected Monday, along with heat index values up to 107 degrees.
—Brayden Garcia, Fort Worth Star-Telegram, 28 July 2025
What Happens Next? CBS Philadelphia also reported that another heat wave is set to take hold between Monday and Wednesday, with highs in the mid to upper 90s and heat indexes of 100 and above.
—Theo Burman, MSNBC Newsweek, 27 July 2025
All of these areas were expected to see heat index values in the triple-digits, according to the NWS.
—Joe Edwards, MSNBC Newsweek, 18 July 2025
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
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
Heat advisories issued for much of the South National Weather Service heat advisories also have been issued across much of the South, with heat index values up to 112 expected across portions of Mississippi, Alabama and Florida.
—John Bacon, USA Today, 28 July 2025
Parts of Mississippi and Louisiana are on alert for heat indices up to 120 degrees.
—Youri Benadjaoud, ABC News, 28 July 2025
High temperatures in the upper 90s to low 100s are expected Monday, along with heat index values up to 107 degrees.
—Brayden Garcia, Fort Worth Star-Telegram, 28 July 2025
What Happens Next? CBS Philadelphia also reported that another heat wave is set to take hold between Monday and Wednesday, with highs in the mid to upper 90s and heat indexes of 100 and above.
—Theo Burman, MSNBC Newsweek, 27 July 2025
All of these areas were expected to see heat index values in the triple-digits, according to the NWS.
—Joe Edwards, MSNBC Newsweek, 18 July 2025
Cite this Entry
“Heat index.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/heat%20index. Accessed 6 Aug. 2025.
Copy CitationLove words? Need even more definitions?
Merriam-Webster unabridged
Share