i live in ontario and in a small town, and we do get cold winters. ive never heard of anyone trying this during winter, but i still dont think it would work. simply becuase you can still get cloud coverage during winter which would fuck ur plan over by using natural radiation. and then of course its just bloody cold. honestly you would have to heat it but im not sure what with. and night time is when it gets coldest, so your heat source would have to make them survive the night.:rastasmoke:

im no pro so if you can do it all the more power to you!:rasta: