Willemstad weather by month
Willemstad runs from about 27°C in January to 30°C in September, with November the wettest month at 112 mm.
warmest month
September
30°C
coolest month
January
27°C
wettest month
November
112 mm
worst air month
June
12 µg/m³
The whole year, month by month.
| Month | Avg temp | Rain | Sun | PM2.5 |
|---|---|---|---|---|
| January | 27°C | 45 mm | 343 h | 6 |
| February | 28°C | 37 mm | 325 h | 11 |
| March | 28°C | 18 mm | 362 h | 8 |
| April | 29°C | 22 mm | 344 h | 8 |
| May | 29°C | 36 mm | 347 h | 11 |
| June | 29°C | 36 mm | 366 h | 12 |
| July | 29°C | 29 mm | 367 h | 9 |
| August | 30°C | 34 mm | 365 h | 9 |
| September | 30°C | 23 mm | 335 h | 8 |
| October | 30°C | 30 mm | 339 h | 7 |
| November | 28°C | 112 mm | 313 h | 7 |
| December | 28°C | 47 mm | 339 h | 7 |
About 4,145 hours of sun a year. Roughly 48 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 2026-05-24. Full method, licences and the list of sources we rejected are on the methodology page.