Although the preferred time to sow grass seed is the late summer or early fall, you can successfully sow grass seed in the winter. This method of sowing grass is called dormant seeding. The grass won't germinate until the following spring when soil temperatures warm. Dormant seeding can be extremely successful. The natural freeze/thaw cycles of spring, combined with ample soil moisture, provide a hospitable environment to germinate grass seeds. Dormant seeding allows the grass to germinate at the first possible opportunity, which enables it to be ready for summer's heat.
Prepare your seedbed in the same manner if you were going to seed in the summer. Till to a depth of 4 to 6 inches. Rake smooth with a garden rake and roll to firm the soil.
Seed your lawn when the soil temperature has fallen below 42 degrees F and is not expected to rise above 50 degrees F for the remainder of the fall and winter. Frosty mornings or right before a predicted snowfall are ideal times to spread the seed.
Fill your spreader up with grass seed. Set the dial on the spreader according to the indicated rate on the grass seed bag.
Walk behind the spreader and push it across the area you wish to sow your grass. Walk all the way across the lawn and all the way back in paths that are next to each other until the entire lawn is covered with your grass seed.
Wait until the following spring when temperatures warm. Watch for germination once the soil temperature reaches about 50 degrees F.