monthly average temperature flagstaff az
- The highest average temperature in Flagstaff is July at 78.2 degrees. The coldest average temperature in Flagstaff is December at 29.6 degrees. The most monthly precipitation in Flagstaff occurs in October with 1 inches.The Flagstaff weather information is based on the average of the previous 3-7 years of data.Loading...he Flagstaff, AZ air quality index is 25.4% less than the Arizona average and 15.5% less than the national average. The Flagstaff, AZ pollution index is the sum of the most hazardous air pollutants displayed in pounds.