heat lightning

So called because it is common on hot summer nights and is sometimes popularly thought to be caused by heat rather storms.

heat lightning (uncountable)

1. Lightning and/or thunder which the observer attributes to heat rather than a storm (e.g. because the storm/rain is too distant to be seen, or because there is no rain, as with dry lighting).
   • 2015 February 9, Hajimu Masuda, Cold War Crucible: The Korean Conflict and the Postwar World, Harvard University Press, →ISBN, page 86:

     Joel Brinkley, a schoolteacher, who was a child in the 1950s, recalled a similar feeling during this era: "It seems surreal now. Every summer, when I heard heat lightning over the city and the sky would light up, I was convinced it was all over. My whole childhood was built on the notion that the Soviets were the real threat."

   • 2015 March 8, Elois Ann Berlin, Brent Berlin, Medical Ethnobiology of the Highland Maya of Chiapas, Mexico: The Gastrointestinal Diseases, Princeton University Press, →ISBN, page 98:

     The beginning of a watery diarrheal event is said to be marked by a great deal of noise, characterized as […] rumbling (tzilelet 'rumbling sound of heat lightning in the rainy season'),  […]

   1. (in particular) Visible lightning that occurs too far away for the resulting thunder to be audible by the observer.
      • 2001, Lee M. Grenci, Jon M. Nese, A World of Weather: Fundamentals of Meteorology: a Text/ Laboratory Manual, Kendall Hunt, →ISBN, page 205:

        The typical range at which thunder can be heard is around 24 km [...] Often, people mistakenly call lightning whose thunder is too far away to be heard "heat lightning," suggesting that the lightning somehow owes its existence merely to the heat of the day and not to a thunderstorm. Nonsense. "Heat lightning" is simply distant lightning whose thunder cannot be heard.

   2. (less commonly) Thunder that is heard without lightning being seen by the observer; heat thunder.
      • 2019 September 3, William Dubay, Don McGregor, Bud Lewis, Eerie Archives Volume 27, Dark Horse Books, →ISBN, page 229:

        THE RAIN FINALLY CAME FROM THE DARK GREY SKIES, SOFT AND TEMPTING AT FIRST, WITH THE SOUND OF HEAT LIGHTNING HOVERING OVER THE SKYSCRAPERS! [image is of a city being rained on, no lightning visible]

      • 2008 July 8, James Lee Burke, Swan Peak: A Dave Robicheaux Novel, Simon and Schuster, →ISBN, page 307:

        Our windows were open, and inside the wind and rumble of heat lightning, I could hear Albert's horses nickering in the darkness.

• sheet lightning