It's a lot more complicated than that. Depends on type of snake, type of thermostat, type of heat source, where the thermometer sensor is, how the enclosure is set up.
Posting a picture of the enclosure may help.
Assuming you're talking about pythons, you want to shoot for a temperature gradient of around low to mid 30s at the warm end and cool at the cold end (generally, room temperature is good, you ideally want it into the mid to low 20s at this time of year, maybe less at night depending on the species, and ideally never above 30, but occasionally slightly above 30 for a short time on hot days shouldn't be a problem. There are many different ways to achieve this depending on what equipment you're using and how you have it set up.