| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 33°F | 25°F | 2.8" |
| February | 18°F | 34°F | 25°F | 2.2" |
| March | 27°F | 46°F | 35°F | 3.3" |
| April | 38°F | 61°F | 48°F | 3.6" |
| May | 47°F | 70°F | 58°F | 4.0" |
| June | 56°F | 77°F | 66°F | 5.4" |
| July | 59°F | 81°F | 70°F | 4.1" |
| August | 58°F | 79°F | 68°F | 4.3" |
| September | 52°F | 73°F | 62°F | 3.5" |
| October | 42°F | 61°F | 51°F | 4.2" |
| November | 32°F | 50°F | 40°F | 3.2" |
| December | 24°F | 38°F | 30°F | 3.6" |
| Index | St. Marys | Pennsylvania | National |
| Air quality index | 35 | 45 | 42 |
| Pollution index | 2,854,150 | 4,584,805 | 2,726,193 |
| Measurement | Total |
| Days measured | 357 |
| Days with good air quality | 345 |
| Days with moderate air quality | 12 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.010% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Brockway, PA | 2,042 | 33 | 34.0% |
| Crenshaw, PA | 320 | 33 | 34.0% |
| James City, PA | 250 | 35 | 30.0% |
| Kersey, PA | 1,022 | 35 | 30.0% |
| Ridgway, PA | 3,781 | 35 | 30.0% |
| St. Marys, PA | 12,333 | 35 | 30.0% |
| City | Population | Air Quality Index | National Avg. |
| New Baltimore, MI | 12,333 | 56 | 12.0% |
| Gulfport, FL | 12,334 | 38 | 24.0% |
| Tamalpais-Homestead Valley, CA | 12,331 | 40 | 20.0% |
| Streator, IL | 12,337 | 0 | 100.0% |
| Lincolnwood, IL | 12,338 | 55 | 10.0% |
| St. Marys, PA | 12,333 | 35 | 30.0% |
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