| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 16°F | 33°F | 24°F | 4.5" |
| February | 16°F | 33°F | 24°F | 5.0" |
| March | 23°F | 41°F | 32°F | 4.4" |
| April | 34°F | 52°F | 43°F | 4.7" |
| May | 44°F | 62°F | 52°F | 5.9" |
| June | 52°F | 69°F | 60°F | 6.7" |
| July | 59°F | 76°F | 67°F | 6.3" |
| August | 57°F | 75°F | 66°F | 5.4" |
| September | 51°F | 69°F | 60°F | 7.3" |
| October | 42°F | 58°F | 50°F | 7.6" |
| November | 32°F | 47°F | 40°F | 7.5" |
| December | 22°F | 37°F | 29°F | 5.4" |
| Index | Castine | Maine | National |
| Air quality index | 36 | 33 | 42 |
| Pollution index | 5,210,570 | 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 | 0.020% |
| Benzene | 0.050% |
| Carbon Tetrachloride | 0.020% |
| Lead | 0.060% |
| Mercury | 0.020% |
| City | Population | Air Quality Index | National Avg. |
| Blue Hill, ME | 1,216 | 31 | 38.0% |
| Searsport, ME | 1,039 | 31 | 38.0% |
| Belfast, ME | 6,710 | 36 | 28.0% |
| Camden, ME | 3,543 | 36 | 28.0% |
| Castine, ME | 813 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Wilton, AL | 813 | 53 | 6.0% |
| Cottondale, FL | 813 | 35 | 30.0% |
| Tignall, GA | 813 | 44 | 12.0% |
| Colfax, IN | 813 | 42 | 16.0% |
| Blackduck, MN | 813 | 29 | 42.0% |
| Castine, ME | 813 | 36 | 28.0% |
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