Vientiane weather by month
Vientiane runs from about 22°C in December to 32°C in April, with September the wettest month at 448 mm.
warmest month
April
32°C
coolest month
December
22°C
wettest month
September
448 mm
worst air month
April
69 µg/m³
The whole year, month by month.
| Month | Avg temp | Rain | Sun | PM2.5 |
|---|---|---|---|---|
| January | 23°C | 30 mm | 314 h | 21 |
| February | 26°C | 2 mm | 311 h | 22 |
| March | 27°C | 46 mm | 313 h | 36 |
| April | 32°C | 53 mm | 341 h | 69 |
| May | 29°C | 265 mm | 283 h | 23 |
| June | 28°C | 437 mm | 240 h | 19 |
| July | 27°C | 421 mm | 231 h | 13 |
| August | 27°C | 409 mm | 243 h | 11 |
| September | 27°C | 448 mm | 228 h | 9 |
| October | 27°C | 115 mm | 335 h | 11 |
| November | 25°C | 11 mm | 312 h | 13 |
| December | 22°C | 0 mm | 304 h | 16 |
About 3,455 hours of sun a year. Roughly 173 rainy days a year.
These are long-run climate normals, not a forecast. A given year can sit well outside them. PM2.5 is a global model: near the coast it counts sea salt as fine particulate and reads high against ground stations, sometimes by a factor of two. Use the shape of the year, not the absolute number.
where these numbers come from
- · Temperature, rainfall and sunshine: ECMWF ERA5 reanalysis climate normals via Open-Meteo (CC BY 4.0), fetched once and stored.
- · PM2.5: Copernicus CAMS reanalysis, monthly means. Modelled, not station readings; near coasts CAMS counts sea salt as PM2.5 and reads high.
Last reviewed 2026-05-23. Full method, licences and the list of sources we rejected are on the methodology page.