I am in a similar position and I have dialed mine right in.
23-28 light's on
20-25 lights off
I gave up and put an old fan heater in the main building, I just estimate the weather and adjust when needed. That hears the main room outside the tents. Then I use tube heaters inside the tent, which are usually IP rated so splash proof or water resistant. All LED.
Also get yorself some insulation baord, as much as you can afford. I just have some offcuts on top of my both tents, to keep the warmth in.
Cover all gaps and draughts, I have a dust sheet around the door which also helps keep it well toaty in there.
If it isn't warm enough for me it certainly isn't for my plants.