You can begin planting pumpkin seeds in the spring after all danger of frost or freezing temperatures has passed. The exact time varies depending on which area of the country you live in. Spring arrives sooner in southern states than in northern states. The USDA Hardiness Chart may help in planning your planting time.
Pumpkin seeds are best planted in the ground after the spring rains have died down and the temperature is at a consistent rate of low seventy's. The alternative is to pot them earlier and then transfer at this time.