| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 19°F | 39°F | 29°F | 3.1" |
| February | 18°F | 40°F | 29°F | 2.8" |
| March | 27°F | 48°F | 37°F | 3.2" |
| April | 37°F | 61°F | 49°F | 3.7" |
| May | 46°F | 71°F | 59°F | 3.4" |
| June | 55°F | 79°F | 67°F | 4.5" |
| July | 61°F | 85°F | 73°F | 3.6" |
| August | 57°F | 83°F | 71°F | 3.6" |
| September | 51°F | 77°F | 64°F | 3.2" |
| October | 41°F | 66°F | 53°F | 4.9" |
| November | 32°F | 55°F | 43°F | 3.6" |
| December | 25°F | 45°F | 34°F | 4.0" |
| Index | Wellesley | Massachusetts | National |
| Air quality index | 43 | 40 | 42 |
| Pollution index | 7,556,320 | 8,399,610 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 291 |
| Days with moderate air quality | 73 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.070% |
| Carbon Tetrachloride | 0.040% |
| Lead | 0.010% |
| Mercury | 0.040% |
| City | Population | Air Quality Index | National Avg. |
| Hopedale, MA | 3,643 | 40 | 20.0% |
| Hopkinton, MA | 3,864 | 40 | 20.0% |
| Maynard, MA | 10,900 | 40 | 20.0% |
| Milford, MA | 26,072 | 40 | 20.0% |
| Cordaville, MA | 2,884 | 40 | 20.0% |
| Wellesley, MA | 28,747 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Summerlin South, NV | 28,716 | 54 | 8.0% |
| Forest Hills, MI | 28,690 | 38 | 24.0% |
| Courtenay, BC | 28,804 | n/a | |
| Vero Beach South, FL | 28,676 | 36 | 28.0% |
| Bella Vista, AR | 28,819 | 44 | 12.0% |
| Wellesley, MA | 28,747 | 43 | 14.0% |
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