Plant grass seed in April. If there is an earlier than usual warming, plant as early as March. If the spring is slow to warm, aim for May. The goal is to disperse the seeds after the last frost but before the weather gets hot.
Take the soil temperature to gauge when it's time to plant grass. Cool-season grass varieties do well when the soil is 50 to 65 degrees Fahrenheit. Warm-season grass seed needs it to be 65 to 70 degrees Fahrenheit.
Keep grass seed consistently moist to encourage the best growth. Moisture will help regulate the soil temperatures and give the roots nutrients to develop.