Depending on the species of lawn grass you are growing and your local climate, lawn grass will either go into dormancy when temperatures drop, or slow its growth rate considerably. In climates where frost or snow is very light and infrequent, lawn grass may need occasional mowing during the winter to keep it at a healthy and attractive blade height. A few guidelines should be observed to prevent damage to the grass plants as well as the soil substrate when mowing in cold weather conditions.
Refrain from mowing your lawn when the grass blades are frozen or even dusted with frost. Wait to mow until the sun has warmed and thawed the blade tissues before mowing to the desired winter blade height for the species.
Wait to mow the lawn after heavy rains or snow to let the grass blades dry off and the soil firm up before running the mower over the surface. Mowing on a muddy lawn can tear out delicate roots, rip blades unevenly and create divots and wheel gouges in the lawn surface that can be felt and will often be visible even after the soil firms and dries.
Remove no more than one-third of the total green blade length in any one mowing session to reduce the harsh cold weather stress on the grass plants. Shorten long overgrown blades with successive weekly mowing sessions to reduce the blade length gradually.