Snow load
Snow that falls in December is often still on the roof in March. That is a load — a sustained one, measured in tonnes on an ordinary house — and it is one of the few things a Minnesota roof carries that most of the country never has to think about.
Weight, and where it collects
Fresh snow is light; snow that has been through a thaw and refrozen is several times heavier for the same depth, and a season’s accumulation compacts as it goes. Modern framing is designed for it, and structural failure on a residential roof is genuinely rare. What is not rare is the load finding the places that were already marginal: an older roof with a spliced rafter, an addition framed lighter than the house, a long span carrying a second roof’s runoff.
The pattern worth knowing is where snow lingers. Shaded north slopes hold it weeks after the south side has cleared. Low-pitched sections shed it slowly or not at all. And wherever a lower roof meets a taller wall, the snow shedding from above lands and stays — the deepest accumulation on most houses is at exactly the junction that also has the most flashing.
What the snow tells you
Snow is a free diagnostic if you read it. A roof where the snow melts evenly and slowly is a roof over a cold, well-vented attic. Bare patches or early melt lines over the living space mean heat is escaping there — the same heat that builds ice at the eaves a few weeks later. And a slope that stays snow-covered while the rest clears is telling you which side of the house never gets sun, which is usually the side whose covering is aging fastest.
Removing snow is rarely worth the risk to the roof or the person doing it. The exceptions are real but narrow: a low-slope section that never sheds, or a roof where the load is landing on a structure that was not designed for it. For the rest, what the snow reveals in February is worth acting on in June.