If you've never been to the Grand Tetons...Go! You can take the trails on the West Side near Driggs Idaho or you can take the trails on the East Side near Jackson Hole Wyoming. Either way the runs' views are stunning.
Early June 2019 and there is still snow if you get up high enough. Otherwise the weather is optimal. Bears could be out, so pack bear spray and preferably go in a large group.
For this run I didn't get to acclimatize. I went with a bunch of past/present crosscountry runners from Teton Valley. We ran 30 minutes out and then came back. I lead the pack up until 26 minutes where I then felt as though my brain was going to Blow! I walked a few feet, people passed, then I felt better and followed. At the turn around point I felt uplifted and had a second wind. I flew down the mountain side at top speeds, all the while wondering why I ever moved away from this place (It is absolutely beautiful). A few of the men beat me to the finish, but I'll get them next time.