In the Northeast, that's probably prior to the cold winter months when your cat is more likely to want to stay inside anyway. This late summer period is a great time to get yourself adjusted to the idea and begin to plan your strategy for the change. By fall your cat may be well into the readjustment. Substitute outside excursions with special play time. Supervised trips to the patio are a good transition.
Cats usually love attention from humans.
Staying indoors may become more welcome if it means getting more love, attention and playtime from you. Praise your cat for using them. Encourage the cat to exercise. Offer toys that are interactive. Cats also enjoy Ping-Pong balls, paper bags, newspapers, and cardboard boxes.