| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 19°F | 34°F | 26°F | 2.6" |
| February | 19°F | 34°F | 26°F | 2.1" |
| March | 28°F | 46°F | 36°F | 2.9" |
| April | 39°F | 60°F | 48°F | 3.3" |
| May | 48°F | 68°F | 57°F | 4.5" |
| June | 57°F | 75°F | 66°F | 5.2" |
| July | 61°F | 79°F | 69°F | 4.5" |
| August | 59°F | 77°F | 68°F | 4.4" |
| September | 53°F | 71°F | 62°F | 4.1" |
| October | 43°F | 60°F | 51°F | 3.9" |
| November | 32°F | 49°F | 40°F | 2.6" |
| December | 24°F | 38°F | 31°F | 3.4" |
| Index | Wellersburg | Pennsylvania | National |
| Air quality index | 36 | 45 | 42 |
| Pollution index | 314,680 | 4,584,805 | 2,726,193 |
| Measurement | Total |
| Days measured | 359 |
| Days with good air quality | 340 |
| Days with moderate air quality | 19 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.004% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Barton, MD | 510 | 36 | 28.0% |
| Klondike, MD | 157 | 36 | 28.0% |
| National, MD | 62 | 36 | 28.0% |
| Shaft, MD | 291 | 36 | 28.0% |
| Barrelville, MD | 44 | 36 | 28.0% |
| Wellersburg, PA | 159 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Pyatt, AR | 159 | 36 | 28.0% |
| Ali Chuk, AZ | 159 | 31 | 38.0% |
| Big Creek, CA | 159 | 60 | 20.0% |
| Calumet, IA | 159 | 35 | 30.0% |
| Shambaugh, IA | 159 | 43 | 14.0% |
| Wellersburg, PA | 159 | 36 | 28.0% |
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