canicular days vs canicule

canicular days and canicule both are nouns.

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

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

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

Other synonyms of canicular days include dog days.

canicular 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