September in Cao Bằng averages a daily high of 31.7°C. Expect roughly 10.7 wet days totalling 138mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Cao Bằng is February–March.
Based on CAO BANG, VM (0.8km), 1995–2024. 20 years of September data.