What is the best season to re-seed your lawn on north east region of USA?

The best season to plant grass seeds is early fall before the soil temperature drops below zero degrees. It will take a few weeks for the new seeds to take root before winter comes. Then when spring comes, the grass will resume growth and become strong enough to sustain the high temperature in the summer. Spring time is actually not a good season to plant, because the grass will not have enough time to grow before harsh summer comes along.