June: Wildflowers bloom in the valley, moose feed in the willows, and snow still frosts the Tetons, the classic postcard look.
September: Aspens and cottonwoods turn gold beneath the Tetons, elk gather and bugle, and summer's crowds are gone by mid-month. Moose rut too.
Permits and reservations
Grand Teton has no entrance reservations or timed entry.
Boat permit: A park boat permit and a state aquatic invasive species (AIS) decal are required to launch a boat on park waters.
Backcountry permits: Required for overnight backcountry trips. Reserve on Recreation.gov, or get a walk-in permit no more than 1 day ahead at a permits office. No permit is needed for day climbs, but overnight stays and bivouacs need one.