Portland weather by month
Portland runs from about 4°C in January to 22°C in July, with January the wettest month at 323 mm.
warmest month
July
22°C
coolest month
January
4°C
wettest month
January
323 mm
worst air month
November
12 µg/m³
The whole year, month by month.
| Month | Avg temp | Rain | Sun | PM2.5 |
|---|---|---|---|---|
| January | 4°C | 323 mm | 89 h | 11 |
| February | 6°C | 172 mm | 159 h | 10 |
| March | 7°C | 135 mm | 230 h | 9 |
| April | 10°C | 80 mm | 254 h | 8 |
| May | 12°C | 104 mm | 328 h | 7 |
| June | 17°C | 47 mm | 350 h | 6 |
| July | 22°C | 7 mm | 423 h | 5 |
| August | 20°C | 18 mm | 357 h | 7 |
| September | 18°C | 46 mm | 300 h | 10 |
| October | 12°C | 155 mm | 224 h | 9 |
| November | 7°C | 276 mm | 130 h | 12 |
| December | 6°C | 269 mm | 121 h | 8 |
About 2,965 hours of sun a year. Roughly 163 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.