Vientiane weather in September
September in Vientiane: sweltering, soaked, with clean air — one of the weakest months to visit.
#11 of 12 months in Vientiane · #576 of 604 destinations to visit in September · comfort 48/100 (tier F)
Updated June 2026 · climate normals from ERA5 reanalysis
Vientiane climate normals — September
| Daytime high | 30°C / 86°F | 🔥 sweltering |
|---|---|---|
| Nighttime low | 24°C / 76°F | |
| Feels like (high) | 36°C / 97°F | |
| Rainfall | 310 mm / 12.2 in | ⛈ soaked |
| Rainy days | 24 days | |
| Humidity | 87% | 💦 very humid |
| Dew point | 24°C / 75°F | |
| Sunshine | 7.9 h/day | |
| Daylight | 12.2 h | |
| Wind | 9 km/h / 5 mph | |
| Air quality (US AQI) | 37 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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Vientiane in September — FAQ
- Is September a good time to visit Vientiane?
- September in Vientiane: sweltering, soaked, with clean air — one of the weakest months to visit. It ranks #11 of 12 months for Vientiane on SeasonMap's comfort score (48/100).
- What is the weather like in Vientiane in September?
- In September, Vientiane averages a daily high of 30°C and a low of 24.2°C, with about 310.1 mm of rain over roughly 24.2 rainy days.
- What is the air quality in Vientiane in September?
- Vientiane has a mean US Air Quality Index of about 37 in September.