From Glossary of Meteorology
An exceptionally hot air mass that develops when high pressure aloft prevents warm air below from rising, thus trapping the warm air as if it were in a dome. The subsidence associated with the high pressure also causes further warming by compression. Heat domes are often associated with calm upper-level flow directly overhead and/or with blocking patterns. The term has been popularized by the news media as a way to explain extreme heat and/or drought events across large regions.
National Ocean and Atmospheric Administration, 2021: What is a heat dome? Accessed 5 October 2021 https://oceanservice.noaa.gov/facts/heat-dome.html.
Term edited 10 September 2018.