| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 26°F | 40°F | 33°F | 10.7" |
| February | 21°F | 34°F | 28°F | 2.7" |
| March | 31°F | 48°F | 40°F | 6.7" |
| April | 39°F | 59°F | 51°F | 4.2" |
| May | 48°F | 71°F | 62°F | 4.3" |
| June | 59°F | 80°F | 72°F | 7.9" |
| July | 63°F | 82°F | 74°F | 6.2" |
| August | 64°F | 82°F | 75°F | 13.8" |
| September | 56°F | 78°F | 69°F | 6.2" |
| October | 47°F | 66°F | 57°F | 6.5" |
| November | 35°F | 53°F | 44°F | 5.9" |
| December | 27°F | 38°F | 33°F | 2.9" |
| Index | Somerset | Pennsylvania | National |
| Air quality index | 36 | 45 | 42 |
| Pollution index | 2,970,510 | 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 | 0.002% |
| Benzene | 0.050% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.650% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Garrett, PA | 430 | 36 | 28.0% |
| Edie, PA | 50 | 36 | 28.0% |
| Casselman, PA | 66 | 36 | 28.0% |
| Rockwood, PA | 802 | 36 | 28.0% |
| Stoystown, PA | 430 | 36 | 28.0% |
| Somerset, PA | 5,888 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Riverside, MD | 5,888 | 46 | 8.0% |
| Morris Plains, NJ | 5,888 | 51 | 2.0% |
| St. James, NC | 5,889 | 34 | 32.0% |
| Attalla, AL | 5,885 | 43 | 14.0% |
| South Lebanon, OH | 5,885 | 54 | 8.0% |
| Somerset, PA | 5,888 | 36 | 28.0% |
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