Portland (Maine) weather by month
Portland (Maine) runs from about -3°C in January to 23°C in July, with March the wettest month at 254 mm.
warmest month
July
23°C
coolest month
January
-3°C
wettest month
March
254 mm
worst air month
August
12 µg/m³
The whole year, month by month.
| Month | Avg temp | Rain | Sun | PM2.5 |
|---|---|---|---|---|
| January | -3°C | 140 mm | 169 h | 6 |
| February | -1°C | 18 mm | 236 h | 9 |
| March | 3°C | 254 mm | 205 h | 7 |
| April | 7°C | 107 mm | 256 h | 7 |
| May | 14°C | 87 mm | 280 h | 7 |
| June | 20°C | 81 mm | 346 h | 9 |
| July | 23°C | 55 mm | 359 h | 11 |
| August | 20°C | 120 mm | 324 h | 12 |
| September | 17°C | 52 mm | 301 h | 7 |
| October | 11°C | 28 mm | 271 h | 4 |
| November | 7°C | 70 mm | 205 h | 5 |
| December | -1°C | 130 mm | 182 h | 5 |
About 3,134 hours of sun a year. Roughly 115 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 2026-05-25. Full method, licences and the list of sources we rejected are on the methodology page.