A customer has a question and I hope we can get some opinions on it, thanks
My question is if growing indoors in a cool climate, what is the best way to keep the temperature even. I currently have winter over here & the box gets as lows as 16 degrees Celsius in the 8 hour rest period with a light on growing temp around 21-23 degrees Celsius. Thank you for your time & help. Bret.
If the lights not providing enough heat, then you’ll want to get a heater set up in there since it’s winter where you are.
Small space heater but if I’m converting this right that is 60°F that is warm enough for them. They can withstand 10°C but not for long periods or it can stunt the growth. I actually have a ac in my room that set on 65 so I wouldn’t wotry about that temp
I use an oil filled radiator. they have two settings for wattage use, and a thermostat. Mine kicks on at 50F. Works great, reliable, and if you use just the lower wattage setting, not too much electricity.
@Donaldj grows in cold conditions lets see if he can give some wisdom 
Your temps sound just fine to me I wouldn’t sweat it until you start dropping below 13-14c you are still in the 60f mark which during dark cycle is fine
I have a 5x5 and all I use is a space heater that has an auto setting. I set the temp and forget about it. Never had an issue and it wasn’t expensive. I just looked around till I found one with the settings that work for me. I ran mine in the mid to upper 70’s in veg then dropped her to 70 for flower. Hope it helps!
I live in central Alaska. I never have issues with the cold, and we keep our house’s heat set at 62F. I don’t use supplemental heating. I also live in a log home. My tents’ temps range from 65F-85F. If anything, my grow room temps sometimes get too high.
I keep my lights on during the day. A lot of people will do lights at night to help heating/cooling issues.
If you go with a heater, make sure you cover any operating lights the unit might have.
I’ve heard the small green lights on equipment is okay during flower, your thoughts? @blackthumbbetty. I have all mine completely covered, too chicken to experiment with it lol 
A heat mat for seedlings will do the trick. Switch it on at lights out.
Green light at night is ok in small doses.