Sun shining in the sky above the clouds

Heat Wave

A Heat Wave is a period of abnormally and uncomfortably hot and unusually humid weather typically lasting two or more days with temperatures outside the historical averages for a given area.

In the National Risk Index, a Heat Wave Risk Index score and rating represent a community's relative risk for Heat Waves when compared to the rest of the United States. A Heat Wave Expected Annual Loss score and rating represent a community's relative level of expected building and population loss each year due to Heat Waves when compared to the rest of the United States.

A map of the United States colored by Heat Wave Risk Index ratings. Heat Wave risk is possible in most non-mountainous terrain, and is most prevalent in eastern Oklahoma, eastern Arkansas, Missouri, southern Illinois, Mississippi, southeastern Kansas, northern Louisiana, southern Arizona, central and southern California, and along the coast in North Carolina. For full results, see the National Risk Index Map webpage.

Heat Wave Exposure

A Heat Wave exposure value represents a community's building value (in dollars) and population (in both people and population equivalence) exposed to Heat Waves.

Heat Wave Annualized Frequency

A Heat Wave annualized frequency value represents the average number of recorded Heat Wave hazard occurrences (event-days) per year over the period of record (12.14 years).

Heat Wave Historic Loss Ratio

A Heat Wave historic loss ratio is the representative percentage of the exposed consequence type value (building or population) expected to be lost due to a Heat Wave hazard occurrence.

Heat Wave Processing Methodology

For comprehensive details about the Heat Wave processing methodology, see the National Risk Index Technical Documentation.