Seed grasses that grow well in warm weather (such as the Southern US and tropical areas) include Bahia, Bermuda, Buffalo and Centipede grasses. Though there are other warm weather grasses, these others are better grown from sod than seed in a home lawn environment. Warm weather grasses are not suitable for environments in which the ground freezes for a significant portion of the winter months, though occasional freezes are rarely harmful.
Grasses that can be seed-planted which are ideal for cold weather climates include Blue Fescue and Rye grasses. These grasses thrive in cooler environments like the Northern US, where the ground may freeze solid for a significant portion of the winter.
Planting in season requires putting the seeds in the ground when the conditions are right for seed germination. For warm weather grass this is the end of spring to the beginning of summer; for cool weather grasses this is the beginning of spring or the beginning of autumn. Seed the grass in the soil to the depth required by your specific seed (usually 1/8 to 1/4 inch) and keep it moist by watering daily until the grass germinates and sprouts.
Grass seed should only freeze when cold weather grass is planted out of season. An acceptable method of planting is to spread the seed over frozen ground toward the end of winter. The freeze-thaw cycle will allow the grass to sink into the ground as cracks develop in the frozen ground and then close up when it thaws. The grass will not be damaged as long as it doesn't germinate prior to freezing. Grass germination happens at approximately 55 degrees Fahrenheit.