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

The 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

Examples of heat index in a Sentence

Recent Examples on the Web

Three Dade Correctional Institution prisoners, represented by the Florida Justice Institute, said in the class-action suit that the state facility’s heat index surpasses 100 degrees in the summer. —Minnah Arshad, USA TODAY, 1 Nov. 2024

Heat risk: Because heat does not pose the same kind of damage to property, CoreLogic defines heat risk as consecutive days exceeding 95 degrees Fahrenheit or temperatures exceeding the 98th percentile of local temperatures, as well as the frequency of extreme heat index days. —Mira Rojanasakul, New York Times, 30 Sep. 2024

Word History

First Known Use

1984, in the meaning defined above