Average weight for one cubic foot of snow is about 15 lbs.
You can expect a wet heavy snow to weigh about twice that, and a light power to weigh 2/3 of that.
So if you have two feet of thick heavy wet snow on top of the rig - it would be about the same pressure as a 120 lb person standing on the roof.
Back 40+ years ago, I have had to go out in a Japanese winter and sweep snow off the wings and tail and fuselage of Navy airplanes. We never started sweeping the snow until it got to about 18 inches deep. And it was a wet thick heavy snow.
Most of the snow was not heavy enough to cause damage, but there are some areas on an airplane where you don't want 50 lbs of weight pushing down.
With typical government efficiency rather than sweep off those areas, we had to clear the snow from the entire aircraft.