canicule

the dog days of late summer; heat wave, hot spell (regardless of the date, and especially when posing a health risk)

“Alors que les épisodes de canicule se multiplient, les risques s’amplifient pour les trains, en particulier à cause de la dilatation des caténaires et des rails.” — As the incidence of heat waves increases, the risks are amplified for trains, in particular due to expansion of overhead cables and rails.

Learned borrowing from Latin Canicula and canicula. From the ancient association of Canicule (“Sirius, Dog Star”) with late summer heat. Doublet of chenille.