San Juan weather by month
San Juan runs from about 25°C in February to 28°C in August, with November the wettest month at 257 mm.
warmest month
August
28°C
coolest month
February
25°C
wettest month
November
257 mm
worst air month
June
10 µg/m³
The whole year, month by month.
| Month | Avg temp | Rain | Sun | PM2.5 |
|---|---|---|---|---|
| January | 26°C | 42 mm | 331 h | 4 |
| February | 25°C | 147 mm | 296 h | 6 |
| March | 25°C | 59 mm | 343 h | 5 |
| April | 26°C | 154 mm | 345 h | 5 |
| May | 27°C | 158 mm | 349 h | 7 |
| June | 28°C | 126 mm | 338 h | 10 |
| July | 28°C | 89 mm | 351 h | 9 |
| August | 28°C | 146 mm | 353 h | 7 |
| September | 28°C | 107 mm | 330 h | 5 |
| October | 28°C | 148 mm | 327 h | 5 |
| November | 26°C | 257 mm | 278 h | 4 |
| December | 26°C | 151 mm | 305 h | 4 |
About 3,946 hours of sun a year. Roughly 160 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.