Think about snakes in the wild where you live, they like to lie on rocks, or in built up areas the roads to absorb the heat, they do this during the warmer months and they brumate during the colder months (meaning they rest and conserve energy and may not eat as much as eating uses energy). So long as they have access to A singular warm spot like herpetology says, the ambient air temperatures aren't as vital. If you find your snake is just CONSTANTLY on the warm spot and doesn't ever want to move (more than for a few days digesting or in shed) then you should consider insulating the enclosure to maintain a bit more heat. Or if your snake is persistently cage surfing (looking like it's constantly trying to escape or get out to a specific side closer to a heat source etc) then again you might want to check your temps and review further options.
Simply put so long as they have a warm area and a cool area they manage their temps and body regulation on their own, you don't want to cook them by not giving them the gradient they need.