When do the leaves change color at Great Sand Dunes? Autumn color changes vary each year due to temperatures, level of cloud cover, and precipitation. There is always some overlap of color changes between elevations and various groves of trees. However, there are general annual patterns that are somewhat predictable. In early September, the first yellow begins to appear in the highest-elevation aspens in Great Sand Dunes National Preserve, visible high on the mountains from the park’s main visitor area. Around the fourth week of September, these subalpine aspen groves are typically at peak color. The golden color slowly works its way down in elevation through September and early October. Late September to early October is generally the peak of color for aspens in higher portions of Mosca Canyon (via Mosca Pass Hiking Trail) and Medano Canyon (via Medano Pass Primitive Road). The first two weeks of October are usually peak for the lowest aspen groves in the foothills of the Sangre de Cristo Mountains, where shrubs such as three-leaf sumac, red osier dogwood, and Rocky Mountain maple also add occasional red color. Montville Nature Trail, not far from the visitor center, is a good location to enjoy a variety of colors during this time. The last trees to peak are the narrow-leaf cottonwood trees along streams such as Medano Creek. Cottonwoods at the base of the mountains turn a deep gold around late September to early October, and the lowest cottonwoods at the base of the dunes reach their peak color in mid-October. Fall has some of the best weather of the year, with generally sunny, calm days and cool nights. Enjoy this special season at Great Sand Dunes! Photo: NPS/Gail Hanley Image description: In this photo taken from the visitor center in late September, higher-elevation aspen groves are at peak yellow color above the dunes, while cottonwood trees along Mosca Creek near the foothills are turning a deep gold color. In the foreground are open grasslands. At top left is the barren summit of Cleveland Peak, and blue sky above with a few white clouds. #GreatSandDunes #Fall #FallColor #Autumn #FallFoliage #FindYourPark