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Boston vs Portland weather: climate comparison
Portland is the warmer of the two, averaging 54°F (12°C) over the year against 51°F (11°C) in Boston. Portland is wetter, with 50.4 in (1280 mm) of precipitation a year to Boston's 45.4 in (1154 mm). Below: every month side by side, from 30 years of ERA5 data (1996–2025).
- Mean temperature
- 10.6°C Boston
12.0°C Portland - Annual precipitation
- 1154.0 mm Boston
1279.7 mm Portland - Rainy days a year
- 121 Boston
146 Portland - Sunshine per day
- 8.6 h Boston
8.5 h Portland
Month by month
| Month | Boston | Portland |
|---|---|---|
| January | 1.9°C | 8.1°C |
| February | 3.5°C | 9.5°C |
| March | 7.5°C | 12.0°C |
| April | 13.5°C | 14.8°C |
| May | 19.1°C | 18.6°C |
| June | 24.4°C | 22.2°C |
| July | 27.9°C | 27.6°C |
| August | 26.9°C | 27.9°C |
| September | 22.9°C | 23.9°C |
| October | 16.5°C | 16.8°C |
| November | 10.2°C | 11.0°C |
| December | 5.0°C | 7.7°C |
Year at a glance
| Measure | Boston | Portland |
|---|---|---|
| Mean annual temperature | 10.6°C | 12.0°C |
| Warmest month (avg high) | Jul · 28°C | Aug · 28°C |
| Coldest month (avg low) | Jan · -7°C | Feb · 2°C |
| Annual range (warmest high − coldest low) | 34°C | 26°C |
| Annual precipitation | 1154.0 mm | 1279.7 mm |
| Rainy days per year | 121 | 146 |
| Wettest / driest month | Mar / Feb | Dec / Jul |
| Average sunshine per day | 8.6 h | 8.5 h |
In short: Portland is the warmest overall (12.0°C mean); Portland gets the most precipitation (1279.7 mm a year); Boston is the sunniest (8.6 h a day on average); Portland has the smallest swing between its warmest and coldest months.
Record high 1996–2025: Boston 40.3°C (2011-07-22), Portland 46.0°C (2021-06-28). Record low: Boston -26.4°C (2016-02-14), Portland -15.3°C (1996-02-02).
Source: Open-Meteo Historical Weather API (CC BY 4.0). Values are ERA5 reanalysis model data on a ~9–25 km grid, not readings from a weather station, so a single town’s thermometer can differ by a few degrees and local showers can be missed. Monthly means of daily ERA5 values, 1996–2025, for the grid cells nearest Boston (42.36, -71.13) and Portland (45.52, -122.64).
Which months differ most?
The gap in average highs is widest in January, when Portland runs 11°F / 6°C warmer, and narrowest in July (1°F / 0°C apart). The biggest rainfall difference is in November: Portland gets 3.8 in (97 mm) more on average.
Add a third or fourth city, or swap in any other place, in the full comparison tool. For one city in depth, see the Boston climate and Portland climate pages.
Compare Boston or Portland with another city
Questions people ask
Is Boston warmer than Portland?
Portland is warmer on average: its mean annual temperature is 54°F (12°C) against 51°F (11°C) in Boston (ERA5, 1996–2025).
Which gets more rain, Boston or Portland?
Portland, with about 50.4 in (1280 mm) of precipitation a year and 146 days with at least 1 mm, compared with 45.4 in (1154 mm) and 121 days in Boston.
Which is sunnier, Boston or Portland?
Boston averages more sunshine: 8.6 h a day against 8.5 h. Sunshine duration is modelled from cloud cover.
How reliable is this comparison?
Both cities use the same 30-year reanalysis, so differences are consistent. Absolute values describe a grid cell several kilometres wide and can differ by a degree or two from the airport station.