Planning for the weather is an important factor for making your trip to Flagstaff a success, especially when you're splurging. The hottest months are usually February and January, with an average temperature of 27°C, while the coldest months are July and August, with an average of 20°C. The rainiest months in Flagstaff are January, March, February and December, with each month seeing an average of 228 mm of rainfall.