Certain types of grass seed can be planted in winter, but not all of them. According to Home Guides, ryegrass, fescue, bluegrass and bentgrass are all considered winter grasses.
According to Grassing, certain types of winter seeds can be planted on top of snow. When grass seeds are planted on top of snow, they fall down into the soil as the snow melts. While winter planting is possible, it is not always successful if the ground is too hard from being frozen. Generally, it is recommended to plant winter grasses in late fall or early winter when the ground is still soft.