| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 16°F | 34°F | 25°F | 2.3" |
| February | 16°F | 35°F | 25°F | 2.1" |
| March | 24°F | 45°F | 34°F | 2.8" |
| April | 35°F | 59°F | 47°F | 3.0" |
| May | 45°F | 71°F | 58°F | 4.0" |
| June | 54°F | 77°F | 65°F | 5.0" |
| July | 59°F | 82°F | 70°F | 4.5" |
| August | 56°F | 79°F | 67°F | 5.0" |
| September | 50°F | 74°F | 61°F | 4.3" |
| October | 41°F | 62°F | 50°F | 4.7" |
| November | 30°F | 50°F | 40°F | 2.4" |
| December | 23°F | 39°F | 31°F | 3.4" |
| Index | Williamstown | Massachusetts | National |
| Air quality index | 35 | 40 | 42 |
| Pollution index | 6,535,100 | 8,399,610 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 345 |
| Days with moderate air quality | 20 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.050% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.090% |
| Mercury | 0.050% |
| City | Population | Air Quality Index | National Avg. |
| Bennington, VT | 8,539 | 35 | 30.0% |
| North Bennington, VT | 1,551 | 35 | 30.0% |
| Old Bennington, VT | 218 | 35 | 30.0% |
| North Adams, MA | 12,897 | 35 | 30.0% |
| Hoosick Falls, NY | 3,361 | 35 | 30.0% |
| Williamstown, MA | 4,565 | 35 | 30.0% |
| City | Population | Air Quality Index | National Avg. |
| Hollister, MO | 4,564 | 18 | 64.0% |
| Rio Communities, NM | 4,566 | 53 | 6.0% |
| Cowichan Valley E, BC | 4,562 | n/a | |
| Portola Valley, CA | 4,568 | 43 | 14.0% |
| Humboldt, IA | 4,568 | 37 | 26.0% |
| Williamstown, MA | 4,565 | 35 | 30.0% |
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