Nice page mrh. What is an "orographic effect"?
As air rises over mountains it cools causing the moisture to fall out. Thats why the west side of the Cascades are so moist and green. The same thing happens in Idaho to a lesser degree. In north Idaho the abrupt rise of the mountains and relatively warm, low elevations creates a local climate similar to western WA, which gives us montane rainforests and species disjunct from the coast.
I don't think you can get to the mountain in May due to snow. Maybe you could bring snow shoes, but the walk would be many miles and require some overnight camping. And as neat as this area is, I wouldn't cut into time at Glacier to come here. Its nice, but come on, Glacier is Glacier!
Just got back from a weekend up there. The last patch of snow in the Larkins L. basin went away while we were there, in the 90-ish degree heat. I imagine there was June access this year, after a relatively dry winter and warm spring and start to summer. A mountain goat almost stumbled over the top of us while my grandson and I were taking a breather on the Goat trail. Nice touch.