I have seeds in milk jugs, outside under the snow, winter sowing. Then I learned the annuals I already put out will likely not make it, as if we have warm snap (like today and tomorrow, close to 60) they may sprout, and then will die from next freeze (next week). But, have extra seeds to resow. I don't have a greenhouse, would have to be a really sturdy one in my winds.
Agree with you Mitch, winds make a BIG difference in the temps and how frozen our ponds get. My goldfish pond has been up and running 100% all winter, except one time the pond got really froze over, and I was afraid the skimmer might not be able to pull water, and when power went out for a day, had to wait to melt hole to start up bubbler again. All is thawing my way, soon no snow to deal with, just mud. But, I'll take it!