We always go to the national parks the week prior to July 4th and the crowds are not back at all. When we were leaving Saturday the 30th the lines to get in the park were huge.
Our experience is that the least busy for the majority of the national parks is when schools are in session...
I went july 2nd and it wasn't bad. Just get there early in the morning.
The park opens on late May, and closes in Oct. July 4 is not the time to go. My best guess would be after school has started.
September. This when most of the college kids and families with k-12 kids have returned to school or you can go just before the closing of Going to the Sun Road (GttSR) for the season. Glacier Park is open in the winter too, but its limited as to what you can do, and GTTSR is closed. TBH once the GTTSR is open its usually busy thanks to social media. If it's still busy during your visit, you can enter the park super early and hit GttSR at 7am or in evening after 6pm and there wont be as many people and you can find parking for hikes.
We are currently touring the area. Yesterday we did GTTSR all the way through. Very pleasant as far as the amount of other tourists go and sharing the space with everyone. I'd say September and the last two weeks have shown we made the best choice but that's not to say the weather will be cooperative when you decide to make the trip. We met one woman who was here last year, said, it rained the whole time. This was her redo- trip. The leaves are changing more each day the temps.are perfect and everyday the sun was shining. It's been magical.
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