You will have a lot of snow. You will likely want to find things to do at the edges of the park and spend a lot of time along the lakes. You will not be able to do much hiking. Perhaps, take a venture a bit north also and see Waterton Lakes in Canada. Go to Flathead Lake outside the park, too.
We went in late May last year and did the Red Bus Tour, great way to see the park. You'll also be close to Whitefish, cute ski town and figure the slopes will still be open (call first)
I guess it depends what you are most interested in. My suggestion is to go the Glacier website. The crews are way behind on snow removal due to record snowfall. The place will be at least 2 weeks behind regular schedule. No matter what, it's a beautiful place to see.
I was going to mention same as Jim up there. Just walking and driving, exploring what looks interesting to you. Just be safe if snow and ledges. They sometimes give way in the spring thaw. Its BEAUTIFUL herr year round. I lived here all my life and still notice something new and cool every day.
Not until Island Oasis opens
They have started to plow the going to the sun road and you may be able to get past lake McDonald lodge. A drive up to Polebridge is worth the drive. Enjoy your time in Montana.
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