| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 13°F | 30°F | 22°F | 2.4" |
| February | 15°F | 33°F | 23°F | 2.3" |
| March | 22°F | 41°F | 31°F | 2.9" |
| April | 35°F | 56°F | 44°F | 4.3" |
| May | 45°F | 67°F | 55°F | 3.7" |
| June | 54°F | 74°F | 63°F | 5.1" |
| July | 60°F | 81°F | 70°F | 3.4" |
| August | 59°F | 79°F | 68°F | 4.3" |
| September | 52°F | 72°F | 61°F | 4.2" |
| October | 42°F | 60°F | 50°F | 6.0" |
| November | 31°F | 48°F | 39°F | 4.2" |
| December | 20°F | 35°F | 27°F | 4.0" |
| Index | Hallowell | Maine | National |
| Air quality index | 28 | 33 | 42 |
| Pollution index | 3,644,290 | 3,417,521 | 2,726,193 |
| Measurement | Total |
| Days measured | 361 |
| Days with good air quality | 356 |
| Days with moderate air quality | 5 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.030% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.030% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Augusta, ME | 18,662 | 28 | 44.0% |
| Richmond, ME | 1,740 | 28 | 44.0% |
| Farmingdale, ME | 2,451 | 28 | 44.0% |
| Gardiner, ME | 5,670 | 28 | 44.0% |
| Winthrop, ME | 2,476 | 28 | 44.0% |
| Hallowell, ME | 2,444 | 28 | 44.0% |
| City | Population | Air Quality Index | National Avg. |
| Jacksboro, TN | 2,444 | 46 | 8.0% |
| Carlisle, KY | 2,443 | 42 | 16.0% |
| Elm Springs, AR | 2,442 | 44 | 12.0% |
| Lavaca, AR | 2,442 | 36 | 28.0% |
| Hamilton City, CA | 2,446 | 46 | 8.0% |
| Hallowell, ME | 2,444 | 28 | 44.0% |
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