| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 23°F | 40°F | 31°F | 3.2" |
| February | 22°F | 41°F | 31°F | 3.2" |
| March | 29°F | 48°F | 38°F | 3.8" |
| April | 40°F | 61°F | 49°F | 3.7" |
| May | 50°F | 69°F | 58°F | 3.8" |
| June | 59°F | 78°F | 67°F | 4.7" |
| July | 66°F | 85°F | 74°F | 4.1" |
| August | 64°F | 83°F | 73°F | 3.5" |
| September | 58°F | 77°F | 66°F | 3.0" |
| October | 48°F | 66°F | 56°F | 5.0" |
| November | 37°F | 55°F | 45°F | 3.3" |
| December | 28°F | 45°F | 36°F | 4.6" |
| Index | Watertown Town | 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. |
| Littleton Common, MA | 3,370 | 40 | 20.0% |
| Framingham, MA | 72,846 | 40 | 20.0% |
| Maynard, MA | 10,900 | 40 | 20.0% |
| Braintree Town, MA | 37,196 | 43 | 14.0% |
| Dover, MA | 2,518 | 43 | 14.0% |
| Watertown Town, MA | 35,749 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Richmond, KY | 35,744 | 33 | 34.0% |
| Cooper City, FL | 35,715 | 41 | 18.0% |
| Foothill Farms, CA | 35,711 | 52 | 4.0% |
| El Mirage, AZ | 35,702 | 74 | 48.0% |
| Temple City, CA | 35,699 | 72 | 44.0% |
| Watertown Town, MA | 35,749 | 43 | 14.0% |
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