Snow-covered farms

When farms in temperate counries are covered by snow and ice, what will the farmers do? I assume that the answer is: Nothing. They wait for the snow to melt before they can till or plant on the soil.

Another case with a different variant is, there are no more snow on the farms, but the lakes, rivers and streams that can irrigate the farms are still frozen, can the farmers still plant? Maybe yes, if they melt by electricity some of the water into their irrigation canal, but that could be expensive, and the farmers will be irrigating super-cold water into their crops. Won't the roots of the crops shrink and wilt? I don't know. A more practical option perhaps, could be to wait for some of those frozen water in the lakes and rivers to also melt naturally.

Of course there are greenhouse farms now, where crops and vegetables are planted under plastic or glass houses, protecting the crops from thick snow and super-cold weather. The enclosed structures trap some of the heat inside, giving some warmth to the leaves, flowers and fruits.