I've been well over 90 and still had them growing fine. Even above 100 or so won't kill them, but it'd probably slow their growth quite a bit. It depends a lot on the breed too, Mandala plants are very heat-resistant, for instance.
khronik Reviewed by khronik on . Temps My growbox temps are always in the 80-85F range. I thought that was high, but then I've read that those might be optimal temps, and my babies are flourishing. I've read your okay up to 95F. Rating: 5