In my experience, winter is generally not the best time to sow grass seed. The cold temperatures and potential for frost can make it difficult for the seeds to germinate and establish strong roots. However, there are some exceptions depending on your climate and the type of grass you're planting. Cool-season grasses like fescue and bluegrass can sometimes be sown in late winter or very early spring before the last frost. But for warm-season grasses like Bermuda and Zoysia, you're better off waiting until late spring when soil temperatures are warmer. A few years back, I tried overseeding my fescue lawn in mid-February. While some of the seeds did sprout, the young grass struggled once we had a cold snap with overnight freezes. Many of the seedlings turned brown and died off. I ended up having to overseed again in April to get good coverage. From that experience, I learned it's best to wait until after the danger of frost has passed to ensure the new grass can firmly establish itself.
The key to winter seeding is timing. Sow the seed when the soil temperature is consistently below 50degF to avoid premature germination. Soil temperatures below that will be too cold and no longer suitable for germinating seeds. Aim for late fall to early winter. In some cases though, snow can actually help act as a natural insulator. It can keep seeds in place and provide moisture as it melts. Winter seeding works best in temperate regions with steady cold winters. In unpredictable climates, wait until early spring for better results. Whatever you do, don't sow on frozen or compacted ground. The seed won't penetrate, and you'll lose it to wind or runoff. Wait for soft, workable soil before seeding.
Winter is ideal for sowing grass seed when there are specific conditions relative to location and climate. Areas that experience thaw and freeze cycles during winter benefit from dormant seeding. This practice helps in regions where the freeze-thaw cycles naturally bury the seeds, enhancing the germination process when the temperatures rise. However, this technique is not effective for locations with a non-moving heavy snow pack or constantly frozen ground. Grass seed does not begin to germinate until the temperatures in the soil reach 10 degrees Celsius. In regions where the temperature remains below this level, germination is not feasible until spring as the soil stays cold for prolonged periods. In some cases, seeds that are exposed too long may die or be washed away. Best time to seed grass in the winter include; Selection of dormant seeding using Kentucky bluegrass or perennial ryegrass in the northern regions. Loosening the soil to prepare it and creating a good seed bed in autumn. Severe erosion conditions where the seeds cannot remain stationary should be avoided. An Ohio landscaper explained that once his dormant seeds were put in the ground, they germinated during the spring thaw and by mid-spring there was thick carpet of grass on the ground. In the end, it all comes down to understanding which seeds are best suited for your region's climate.