The busiest times of year are spring and fall. In the spring blooming wildflowers herald the end of winter, and temperatures in the 70s bring the year's largest crowds. The crowds remain steady in summer as the thermostat approaches 100°F and above in July and August. Sudden dramatic cloudbursts create rainfalls over red rock walls in late-summer "monsoon" season.
Fall weather is perfect—clear, warm days and crisp, cool nights. The park is much quieter in winter, and from December through February you can hike many of the trails in relative solitude. Snow seldom falls in the valley beneath the La Sal Mountains, and when it does, Arches is a photographer's paradise, as snow drapes slickrock mounds and natural rock windows.