64f lights out is good for most strains. Keeping in mind that different strains have different preferences, you want between 62 and 72 F lights off, 68 to 77 F lights on, with catastrophic damage possible for most strains above 85F. (Keeping roots cool and/or adding CO2 can increase the upper limit, buts that's advanced material I'm just starting to play with, I'll let others do the talking there).Enditall, keep in mind im fighting the cold as well... seeing 64f with the light out... trying to balance room temps and the tent temps, one big cluster (of not a bud)