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Boston vs San Francisco weather: climate comparison
San Francisco is the warmer of the two, averaging 57°F (14°C) over the year against 51°F (11°C) in Boston. Boston is wetter, with 45.4 in (1154 mm) of precipitation a year to San Francisco's 20.3 in (515 mm). Below: every month side by side, from 30 years of ERA5 data (1996–2025).
- Mean temperature
- 10.6°C Boston
14.0°C San Francisco - Annual precipitation
- 1154.0 mm Boston
514.5 mm San Francisco - Rainy days a year
- 121 Boston
56 San Francisco - Sunshine per day
- 8.6 h Boston
10.5 h San Francisco
Month by month
| Month | Boston | San Francisco |
|---|---|---|
| January | 1.9°C | 13.6°C |
| February | 3.5°C | 14.4°C |
| March | 7.5°C | 15.5°C |
| April | 13.5°C | 16.6°C |
| May | 19.1°C | 18.3°C |
| June | 24.4°C | 20.2°C |
| July | 27.9°C | 20.5°C |
| August | 26.9°C | 21.2°C |
| September | 22.9°C | 22.0°C |
| October | 16.5°C | 20.5°C |
| November | 10.2°C | 16.4°C |
| December | 5.0°C | 13.5°C |
Year at a glance
| Measure | Boston | San Francisco |
|---|---|---|
| Mean annual temperature | 10.6°C | 14.0°C |
| Warmest month (avg high) | Jul · 28°C | Sep · 22°C |
| Coldest month (avg low) | Jan · -7°C | Jan · 7°C |
| Annual range (warmest high − coldest low) | 34°C | 15°C |
| Annual precipitation | 1154.0 mm | 514.5 mm |
| Rainy days per year | 121 | 56 |
| Wettest / driest month | Mar / Feb | Dec / Jul |
| Average sunshine per day | 8.6 h | 10.5 h |
In short: San Francisco is the warmest overall (14.0°C mean); Boston gets the most precipitation (1154.0 mm a year); San Francisco is the sunniest (10.5 h a day on average); San Francisco has the smallest swing between its warmest and coldest months.
Record high 1996–2025: Boston 40.3°C (2011-07-22), San Francisco 38.5°C (2017-09-02). Record low: Boston -26.4°C (2016-02-14), San Francisco -2.3°C (1998-12-21).
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 San Francisco (37.79, -122.41).
Which months differ most?
The gap in average highs is widest in January, when San Francisco runs 21°F / 12°C warmer, and narrowest in May (1°F / 1°C apart). The biggest rainfall difference is in September: Boston gets 3.5 in (90 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 San Francisco climate pages.
Compare Boston or San Francisco with another city
Questions people ask
Is Boston warmer than San Francisco?
San Francisco is warmer on average: its mean annual temperature is 57°F (14°C) against 51°F (11°C) in Boston (ERA5, 1996–2025).
Which gets more rain, Boston or San Francisco?
Boston, with about 45.4 in (1154 mm) of precipitation a year and 121 days with at least 1 mm, compared with 20.3 in (515 mm) and 56 days in San Francisco.
Which is sunnier, Boston or San Francisco?
San Francisco averages more sunshine: 10.5 h a day against 8.6 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.