| 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 | Johnstown | Pennsylvania | National |
| Air quality index | 39 | 45 | 42 |
| Pollution index | 2,970,510 | 4,584,805 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 296 |
| Days with moderate air quality | 69 |
| 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. |
| Boswell, PA | 1,415 | 36 | 28.0% |
| Jennerstown, PA | 1,172 | 36 | 28.0% |
| Laurel Mountain, PA | 125 | 36 | 28.0% |
| Black Lick, PA | 1,416 | 38 | 24.0% |
| Graceton, PA | 160 | 38 | 24.0% |
| Johnstown, PA | 19,381 | 39 | 22.0% |
| City | Population | Air Quality Index | National Avg. |
| Yorkville, IL | 19,386 | 0 | 100.0% |
| Matteson, IL | 19,374 | 55 | 10.0% |
| Angleton, TX | 19,371 | 52 | 4.0% |
| Langley Park, MD | 19,391 | 47 | 6.0% |
| Montrose, CO | 19,396 | 44 | 12.0% |
| Johnstown, PA | 19,381 | 39 | 22.0% |
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