I guess that would depend on what species of snakes you're talking about. Most colubrids don't mind the colder temps so much if they have a place to warm up. But ball pythons would NOT do well if the temps in their enclosure are dropping into the 60's....even if they do still have a warm spot. Snakes aren't real bright and they will let themselves get too cold. They don't have interior thermometers that tell them "Oops, this spot is too cool (or too hot), might not be smart to lay here."
Our responsibility as keepers is to make sure their enclosures are set at optimum temps at all times.