they associate heat to the bright white of the sun. You should try and replicate this. Provide a white/cream coloured light as a basking spot. UVB tube is also needed.
The temp can go below 24. I would leave them overnight without heat unless your house temps fall below 15celcius. There should be no light at all on at night time. Keep it simple just like a nice normal sunny day..10 or so hours of sunshine. Otherwise you risk bothering their sleeping patterns which can stress them out. Your basking temp for babies should be 40-45degrees celcius.
If by the odd chance that there is a cold period of weather just put a small room heater and switch on for a few mins just to take the chill out of the air