| 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 | West Mifflin | Pennsylvania | National |
| Air quality index | 56 | 45 | 42 |
| Pollution index | 889,808 | 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 | 0.001% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.030% |
| Mercury | 0.030% |
| City | Population | Air Quality Index | National Avg. |
| Herminie, PA | 108 | 56 | 12.0% |
| Bridgeville, PA | 4,939 | 56 | 12.0% |
| Adamsburg, PA | 138 | 56 | 12.0% |
| Jefferson Hills, PA | 11,166 | 56 | 12.0% |
| Crafton, PA | 5,810 | 56 | 12.0% |
| West Mifflin, PA | 19,742 | 56 | 12.0% |
| City | Population | Air Quality Index | National Avg. |
| Niskayuna, NY | 19,741 | 37 | 26.0% |
| Shafter, CA | 19,743 | 67 | 34.0% |
| Sherwood, OR | 19,745 | 38 | 24.0% |
| Mont-Saint-Hilaire, QC | 19,745 | n/a | |
| Blythe, CA | 19,747 | 13 | 74.0% |
| West Mifflin, PA | 19,742 | 56 | 12.0% |
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