the.com/heatwave

means A prolonged stretch of excessively hot weather, often with high humidity, lasting days or longer.

from A transparent compound of "heat" and "wave" — heat from Old English hætu (the quality of being hot), and wave borrowed from the imagery of the sea, the idea of warmth rolling in like a swell. The metaphor of weather arriving in "waves" took hold in 19th-century English, when newspapers and the new science of meteorology needed a word for the way oppressive heat seemed to surge across regions, crest, and recede. "Cold wave" appeared in much the same spirit, both treating temperature as something tidal — coming in great, sweeping movements rather than sitting still.