77F is fine as long as you have a 90F hot spot for them. I keep all my snakes' cool sides around 78-80F once the ReptiChips dry out some. When I first put it in though, the cool sides all drop down around 77-78F. That 75F though on the recorded low is the max I would want to let it get. And the high of 81F? That's a pretty big swing lol.