Where to go in September, maybe October

The first two weeks of September is perfect for Yellowstone and the Grand Tetons. Even the park's campgrounds are still open. Everything doesn't close at that time. Slowly work your way south into Utah and Arizona for October and your drive back.

No experience with October, but we have been to Yellowstone, Grand Teton and Glacier in September with no issues with snow. September is popular for those folks who don't have school age kids, so most facilities should be open. Easy to check ahead.

Jackson Hole Airport is a lot closer to Yellowstone than Boise.

The bull Elk will have full racks in September and will be bugling to attract their harems. The bull Moose will also have full racks. We often see Moose along the Gros Ventre River just south of the Gros Ventre Campground in Grand Teton.

Crowe.. September is absolutely the best time to do an Oregon/Washington Coast trip. Best weather of the entire year and school is back in session..wide open at the State Parks

Most everything in the Rockies will be shutting down shortly after Labor day, and weather will be getting cooler. By October you could see snow for sure, and definitely cold. Yellowstone should have some stuff still open, of course the gysers dont pay attention to the seasons. If your flying/driving, fly into Boise, rent your car. Then you could hit Yellowstone, north to MT Rushmore, loop back to Glacier, and back to Boise