At a Glance
- Avg High: ~64°F
- Avg Low: ~36°F
- Aspen Color: Late Sept peak
- Elk Rut: Active
September — The Best-Kept Month
September is arguably Grand Lake's finest month, and it's consistently underbooked relative to its quality. Summer crowds are gone, temperatures are comfortable for all outdoor activities, and aspen color begins building through the month — peaking in the last two weeks of September at higher elevations and early October in the valley.
Elk rut season begins in September. Bull elk bugle at dawn and dusk — one of the most dramatic natural sounds in North America. The meadows near the RMNP west entrance and along the Colorado River corridor are reliable elk viewing spots. The west-side entrance sees far fewer viewers during rut season than the crowded Horseshoe Park area on the east side.
Fall Color Timing
Aspen color in Grand County typically begins at higher elevations (above 10,000 feet) in mid-September and moves to lower elevations through late September and into early October. Timing varies year to year based on temperature and precipitation. The drive on Highway 34 through RMNP toward the Alpine Visitor Center in late September is one of Colorado's finest fall color routes.
The combination of gold aspen, evergreen spruce and fir, and the blue sky of September creates a color palette that summer visitors never see. Fall photography in and around Grand Lake is exceptional in the last two weeks of September.
September Outdoor Activities
All RMNP trails are still fully open in September. Timed entry permit requirements typically end in mid-September — check nps.gov/romo for current year dates. Fishing is excellent in September as kokanee salmon continue their run and trout become more active in cooling water temperatures.
Kayaking remains accessible through September, with morning conditions typically calm and water still comfortable for paddling. The Arapaho National Recreation Area trails around Lake Granby and Monarch Lake have excellent fall color and see minimal crowds.