Snow cover is mostly good for a dormant lawn, because it insulates the crown against repeated freezing and thawing. The damage that does occur under snow comes from three things: snow mold on turf that went into winter too long or covered in leaf litter, compaction from traffic across frozen ground, and voles tunneling at the soil surface.
What actually happens to your lawn under the snow
Snow arrives Friday and will be around for a while. Here is what is actually going on underneath it, which is more interesting than most people expect and occasionally expensive.
Snow is mostly protecting your lawn
A consistent snow cover holds the ground at a far more stable temperature than bare exposed turf. Grass without snow on it goes through freezing and thawing repeatedly all winter, and that cycling is harder on a dormant plant than simply being covered and left alone. A winter with reliable snow is usually a better winter for turf than a cold, dry, bare one.
What does cause damage, starting with snow mold
Snow mold is a fungal problem that develops under prolonged snow cover, and it needs specific conditions to take hold. Turf that went into dormancy too long, or turf matted down under leaf litter, holds moisture against the crown for months. That is the environment it wants.
It shows up when the snow goes, as matted, straw colored, slightly crusted patches, often in circles. Most lawns recover from it once the area is raked open and allowed to dry and breathe, and most people never need to do anything beyond that. A bad case thins the turf enough to need overseeding in spring.
Everything that prevents it happens before the snow arrives, which is why it is worth knowing now rather than in March. A final cut shorter than summer height, and leaves cleared off the grass rather than just off the driveway. That is essentially the whole prevention strategy.
Traffic, which is the one people cause themselves
Walking, parking, or driving across frozen or snow covered turf crushes crowns that cannot repair themselves until growth resumes. The damage is invisible until April, when it reappears as a path shaped exactly like the route somebody took in November.
The same applies to where snow gets piled. A large pile sitting on turf stays frozen for weeks after everything around it has thawed, and that area comes out of winter last and weakest. Worth a moment's thought about where it goes before the first time you move it, because the first spot usually becomes the permanent one.
Voles, which nobody warns people about
This is the one that surprises homeowners here. Under snow cover, voles tunnel along the soil surface, protected from predators and insulated from the cold, and they chew runways through turf and strip bark from the base of young trees and shrubs.
You will not see any of it until the snow melts, and then it appears all at once as a network of surface trails across the lawn, usually two inches or so wide. Turf damage generally fills back in over the season. Girdled bark on a young tree can kill it outright, and that one does not recover.
Prevention is unglamorous and effective. A short final cut gives them less cover. Pulling mulch back from the base of trunks removes the sheltered runway they prefer. A guard on young trees handles the part that actually matters.
What to do between now and spring
Mostly nothing, which is the honest answer. Stay off the frozen grass, think about where the snow goes, and resist the urge to do anything to a dormant lawn.
Then take a walk in early April before anyone touches anything, and look for the matted patches, the paths, and the surface trails. What you find in that first week tells you more about what the property needs than anything else you could do, and it is the one assessment nobody ever makes.
Generally no. A consistent snow cover insulates dormant turf and protects it from repeated freezing and thawing, which is harder on the plant than being covered. Damage under snow comes from snow mold, traffic across frozen ground, and voles rather than from the snow itself.
A fungal problem that develops under prolonged snow cover where moisture is trapped against the crown, typically on turf left too long before dormancy or matted under leaf litter. It appears in spring as matted straw colored patches. Prevention happens before snowfall: a shorter final cut and clearing leaves off the grass.
Usually voles. Under snow cover they tunnel along the soil surface, sheltered from predators and cold, chewing runways through the turf. The trails appear all at once when snow melts. Turf normally recovers, but bark stripped from young trees often does not.
Avoid it where possible. Traffic across frozen or snow-covered turf crushes crowns that cannot repair until growth resumes, and the damage shows in spring as visible paths. The same applies to repeatedly piling snow in one spot on turf.