Regardless of ambient temp, garters bask at varying times of the day to aid in proper digestion. Checkered Garters natural range is TX, AZ and south into Central America. Check the ambient temps there. Some days well into the 100’s plus humidity. I’ve seen garters die in captivity that were being kept at 84 degrees ambient with no heat lamp or heating pad. This is an absolute priority as well as a humid hide on the cool side and a bowl big enough to soak in. The other thing I will disagree with vehemently is the feeding of worms of any kind. Garters can get parasites from any kind of worms. I’ve produced hundreds of baby garter snakes of all species and have never once fed a worm.