English
heat storm
From heat + storm.
Proto-Indo-European *keHy- ‘heat’
Proto-Germanic *haitį̄
Proto-West Germanic *haitī
Old English hǣtu
Middle English hete ‘heat’
English heat
Proto-Germanic *staurijaną ‘to destroy, disturb’
Proto-Germanic *sturmaz ‘storm’
Proto-West Germanic *sturm ‘storm’
Old English storm ‘tempest, storm’
Middle English storm
English storm
Today it means
noun An extended heat wave, defined as high temperatures over 100 degrees Fahrenheit over a large area for three consecutive days.
Language periods are conventional ranges, not dates for this word.
Etymograph / heat storm