Let it snow, let it snow

This year, Mr. Winter has a pretty strange behavior, here in Quebec. We had a lot of snow, and no warm periods that usually let the snow melt down and provide our so delightfull winter mud. No, all the fallen snowflakes are still here. Consequently, all the city snow repositories are full and Montreal has to open new ones. But also, a couple of houses were crunched by the weight of the snow on their roofs. That's a total mystery to me. When I was young, at primary school, I remember clearly the teacher saying that on countrysides having a lot of snow, the roofs were sharp to let snowflakes slipping alongside. But here in Montreal, most of the roofs are flat. If someone has an explanation, please let me know.