Here's what happened to our hoop house after we got six inches of drifting snow:
What you're seeing here is that one side of the hoops is held up by the garage, but it's collected snow on top of it, bending it horizontal. That introduced slack into the other side, which collected snow from the bottom up. Nonetheless, the roof held, and the greenhouse effect was alive and well. When I got in there, the outside temperature was 0˚F and inside was about 60˚F. By the time I had the snow cleared off, it was 80˚F inside! Here's what the outside looked like before I started clearing the snow off.
Most of the hoops recovered, but a few of them broke and will have to be patched up when we get a warm day.