grow tent in colder climate

Hey, I'm in a similar situation. Unfortunately I think you're gonna need a way to keep the temperature of your tent up. Lights definitely won't be enough in a garage, seriously you will need a heater. I got myself an ac infinity thermoforge t3 heater and basically never have to worry about it again. It's a small investment compared to how much peace it brings you to know your plants are warm and happy. Good luck!

Then go for autos, as longer day will secure needed temps, go for cheap sink led lights, something like TS series from Mars Hydro and you should be ok. Heating mats are good for seedlings, have a feeling, that it will bring more troubles with developed plants. Go for 20/4 light schedule ( i still think that 18/6 is optimal, but here you need to adapt.). I did grow in basement, with really low temps, struggled a lot, heater was a must during night time, but i went with photo dependant ... Day time normally is warmer, so make theirs night during humans day.

It will be fine if you have to lights on when at coldest, normally night-time.. greenhouse tube heaters are the best price to buy and run and safe...have them slightly off the floor to keep the soil warmer... Good luck pal. Inbox for more advice