dog days vs canicule

dog days and canicule both are nouns.

Word	Noun	Adjective	Verb	Adverb
dog days	Yes	No	No	No
canicule	Yes	No	No	No

As nouns, dog days and canicule are synonyms defined as:

dog days and canicule: the hot period between early July and early September; a period of inactivity

Other synonyms of dog days include canicular days.

dog days (noun)	canicule (noun)
the hot period between early July and early September; a period of inactivity	the hot period between early July and early September; a period of inactivity