Visit October through early May to miss the stifling summer heat. Places like the Grand Canyon and Monument Valley, which are exceedingly popular in the summer, will be quieter in late spring or early fall. If your trip does fall during the summer months, the Mogollon Rim highlands are a cool relief from the heat. Meanwhile, Flagstaff is the perfect winter playground. If you have a winter road trip in mind, remember that snowy road closures are common at higher elevations. No matter when you visit, be prepared for cold nights everywhere in the state.