September in Chiang Mai averages a daily high of 32.4°C. Expect roughly 20.9 wet days totalling 284.7mm. Demanding conditions — pack for it and plan indoor options.
Across the year, the best time to visit Chiang Mai is December–January.
Based on CHIANG MAI, TH (0.8km), 1995–2024. 17 years of September data.