| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 13°F | 34°F | 24°F | 3.3" |
| February | 14°F | 35°F | 25°F | 3.2" |
| March | 23°F | 43°F | 33°F | 3.7" |
| April | 34°F | 56°F | 44°F | 3.3" |
| May | 44°F | 66°F | 54°F | 3.7" |
| June | 53°F | 73°F | 62°F | 5.6" |
| July | 59°F | 80°F | 69°F | 4.1" |
| August | 57°F | 79°F | 67°F | 3.6" |
| September | 50°F | 72°F | 61°F | 3.9" |
| October | 40°F | 61°F | 50°F | 6.0" |
| November | 30°F | 50°F | 39°F | 4.5" |
| December | 20°F | 38°F | 29°F | 4.9" |
| Index | Newcastle | Maine | National |
| Air quality index | 36 | 33 | 42 |
| Pollution index | 2,415,390 | 3,417,521 | 2,726,193 |
| Measurement | Total |
| Days measured | 213 |
| Days with good air quality | 204 |
| Days with moderate air quality | 9 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.004% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.003% |
| Lead | 0.010% |
| Mercury | 0.002% |
| City | Population | Air Quality Index | National Avg. |
| Randolph, ME | 1,711 | 28 | 44.0% |
| Richmond, ME | 1,740 | 28 | 44.0% |
| Farmingdale, ME | 2,451 | 28 | 44.0% |
| Gardiner, ME | 5,670 | 28 | 44.0% |
| Wiscasset, ME | 1,293 | 28 | 44.0% |
| Newcastle, ME | 643 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Santa Rosa, AZ | 643 | 47 | 6.0% |
| Acacia Villas, FL | 643 | 41 | 18.0% |
| Tower Hill, IL | 643 | 40 | 20.0% |
| Park City, KY | 643 | 43 | 14.0% |
| Biwabik, MN | 643 | 35 | 30.0% |
| Newcastle, ME | 643 | 36 | 28.0% |
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