| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 23°F | 40°F | 32°F | 3.1" |
| February | 23°F | 40°F | 31°F | 2.7" |
| March | 30°F | 47°F | 38°F | 4.2" |
| April | 39°F | 58°F | 48°F | 3.8" |
| May | 49°F | 67°F | 57°F | 4.1" |
| June | 58°F | 75°F | 66°F | 4.3" |
| July | 65°F | 82°F | 73°F | 3.7" |
| August | 62°F | 80°F | 71°F | 3.1" |
| September | 56°F | 75°F | 65°F | 3.6" |
| October | 46°F | 65°F | 55°F | 4.3" |
| November | 37°F | 55°F | 45°F | 3.1" |
| December | 29°F | 46°F | 37°F | 4.4" |
| Index | Charlestown | Rhode Island | National |
| Air quality index | 37 | 45 | 42 |
| Pollution index | 2,960,790 | 3,440,259 | 2,726,193 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 323 |
| Days with moderate air quality | 34 |
| Days w/ poor A.Q. for sensitive groups | 7 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.003% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.020% |
| Mercury | 0.005% |
| City | Population | Air Quality Index | National Avg. |
| Hopkinton, RI | 612 | 37 | 26.0% |
| Pawcatuck, CT | 5,024 | 37 | 26.0% |
| Westerly, RI | 17,842 | 37 | 26.0% |
| Quonochontaug, RI | 422 | 37 | 26.0% |
| Ashaway, RI | 1,444 | 37 | 26.0% |
| Charlestown, RI | 1,392 | 37 | 26.0% |
| City | Population | Air Quality Index | National Avg. |
| Forreston, IL | 1,392 | 42 | 16.0% |
| Hoopers Creek, NC | 1,392 | 44 | 12.0% |
| Milroy, PA | 1,392 | 44 | 12.0% |
| Jarrell, TX | 1,392 | 42 | 16.0% |
| Macpherson-Grizzly Valley, YT | 1,392 | n/a | |
| Charlestown, RI | 1,392 | 37 | 26.0% |
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