August in Flagstaff averages a daily high of 26.2°C with nights around 10.5°C. Expect roughly 13.3 wet days totalling 77mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Flagstaff is May–June.
Based on FLAGSTAFF AIRPORT, AZ US (6.1km), 1995–2024. 30 years of August data.