| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 38°F | 30°F | 3.2" |
| February | 23°F | 39°F | 30°F | 2.2" |
| March | 32°F | 52°F | 41°F | 3.4" |
| April | 43°F | 65°F | 53°F | 3.4" |
| May | 52°F | 74°F | 62°F | 4.2" |
| June | 60°F | 81°F | 70°F | 5.1" |
| July | 64°F | 84°F | 73°F | 5.1" |
| August | 63°F | 82°F | 72°F | 4.1" |
| September | 56°F | 77°F | 66°F | 3.1" |
| October | 46°F | 65°F | 54°F | 3.8" |
| November | 35°F | 54°F | 44°F | 2.8" |
| December | 28°F | 43°F | 35°F | 3.7" |
| Index | Upper St. Clair | Pennsylvania | National |
| Air quality index | 56 | 45 | 42 |
| Pollution index | 2,548,030 | 4,584,805 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 129 |
| Days with moderate air quality | 220 |
| Days w/ poor A.Q. for sensitive groups | 12 |
| Days with unhealthy air quality | 4 |
| Pollutant | Total |
| Arsenic | 0.220% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.050% |
| Mercury | 0.020% |
| City | Population | Air Quality Index | National Avg. |
| Westland, PA | 45 | 46 | 8.0% |
| Hickory, PA | 542 | 46 | 8.0% |
| Clinton, PA | 1,049 | 46 | 8.0% |
| Wolfdale, PA | 3,097 | 46 | 8.0% |
| Joffre, PA | 410 | 46 | 8.0% |
| Upper St. Clair, PA | 19,521 | 56 | 12.0% |
| City | Population | Air Quality Index | National Avg. |
| Montgomery, IL | 19,515 | 0 | 100.0% |
| Salmon Creek, WA | 19,506 | 38 | 24.0% |
| El Reno, OK | 19,539 | 48 | 4.0% |
| Monroe, MI | 19,543 | 1 | 98.0% |
| Lake Forest, IL | 19,497 | 55 | 10.0% |
| Upper St. Clair, PA | 19,521 | 56 | 12.0% |
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