June is the busiest month, when the Manti Pageant draws large crowds to the temple grounds. Book lodging well in advance if you plan to visit during pageant week. The rest of summer is quiet and warm, with temperatures in the 30s Celsius on valley days.
September and October are the best months for the surrounding forest: aspen colour peaks in late September, and the daytime heat drops to something more manageable. Winters are cold and the high roads into the national forest close with snow.