Turning the heat sources off is a great start. It seems like the obvious one, but not everyone remembers to.
I would make sure they have access to a larger water bowl than usual.
You can also take something like a frozen water bottle and wrap it in a hand towel. I would put that in a ziplock bag to make sure the snake can't unwrap the towel and contact the ice directly. But it should offer a cool enough spot for them to thermoregulate a bit to a cooler temp.
Sorril basically tackled all of the symptoms to watch out for. We just ended a nasty heatwave here. I hope yours lets up soon