Arizona does not observe daylight savings. You are on Mountain Standard Time. Leave Flagstaff with a full tank of gas and food as there are no services at the monuments. The park is open year round. Expect windy conditions most of the year.
Spring is usually mild but heavy snowfall can occur.
Summer days are warm with temperatures in the eighties. Afternoon thunderstorms likely July to September. In winter, snow and freezing temperatures alternate with mild weather. Nearest commercial airport is located in Flagstaff, Arizona. The visitor center and portions of the Lava Flow Trail are accessible.