Six inches on the driveway this morning
Waking up to snow on a new slab feels like it should be worse than it is. Snow itself is light. A foot of it spread across a driveway weighs far less than the truck that will eventually park on top of it, and concrete is built to carry weight, not to be bothered by a soft blanket sitting on the surface overnight.
If anything, a layer of snow works a little bit in the concrete's favor on a cold night. It insulates the surface from the sharpest swing in air temperature the same way a blanket would, which is why bare, cured concrete under fresh snow is not usually the part of a winter storm worth worrying about.
The exception is concrete that has not finished curing
The picture changes if the slab is still new, meaning it went down in the last few weeks and has not reached the point where curing is essentially done. Concrete that young is still building strength and is more sensitive to water sitting on it and soaking in than concrete that finished curing months ago.
Snow that sits and melts slowly on a young slab, then refreezes overnight as the temperature drops again, puts that surface through more freeze and thaw cycling in a short window than it would otherwise see. Repeated cycling on a surface too new to defend itself is how scaling starts, a thin flaking of the top layer, so a slab that goes down right before winter is one we may cover with a curing blanket ahead of a snow event rather than leave it to work through the melt and refreeze on its own.
What actually scratches or stains a new surface
The snow itself is rarely the problem. How it gets cleared off is where a new slab is more likely to pick up a mark. A metal shovel blade dragged straight across a broom finished surface, especially one still relatively fresh, can scuff or lightly scratch the top in a way a plastic blade will not.
The same goes for anything left sitting under the snow. A car parked with a slow oil drip, a mower left out, or metal furniture legs are all more likely to leave a stain on concrete that is still porous from being new than on a slab that finished curing a season or two back, since anything sitting on the surface has longer to soak in before the concrete has closed up.
- Use a plastic shovel blade on new concrete, not a metal one
- Keep vehicles and equipment with fluid leaks off a snow covered new slab
- Let repeated melt and refreeze happen without adding anything to speed it up
- Watch for standing meltwater that is not draining the way the rest of the slab does
What is actually worth a call after a snowy stretch
A hairline crack running along a control joint, some surface dust after the first sweep, or minor color variation are all normal and not something a snowstorm caused. What is worth calling about is different: a section of slab that looks like it has settled compared to the rest, a crack that runs away from the joint across open concrete, or standing water that is not draining once the snow is gone the way it did right after the pour.
Those point at something happening under the slab rather than anything the weather did to the surface, and they are worth a look regardless of the season.