You can inspect the rafters and trusses and if they are bending downward or flexing to the side, the roof is in danger, he says. Unless you can get a recommendation from a friendly engineer or a building official in your city, the decision to shovel off a roof will be based on an educated guess, Hellevang says. If you do decide to shovel off your roof, remember that snow and ice can make the job dangerous. Agricultural buildings with their metal roofs can be especially treacherous. And power lines can be an added hazard.
Cold temperatures make shingles brittle so they break easier.
You're also more likely to remove many of the little pebbles from the surface of the shingles, shortening the life of your roof.