| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 19°F | 37°F | 28°F | 2.8" |
| February | 19°F | 39°F | 29°F | 2.5" |
| March | 27°F | 49°F | 37°F | 3.0" |
| April | 38°F | 64°F | 50°F | 3.3" |
| May | 48°F | 74°F | 60°F | 3.2" |
| June | 57°F | 81°F | 69°F | 4.2" |
| July | 61°F | 86°F | 73°F | 3.7" |
| August | 59°F | 83°F | 71°F | 4.0" |
| September | 53°F | 77°F | 64°F | 3.5" |
| October | 43°F | 65°F | 53°F | 4.9" |
| November | 33°F | 53°F | 43°F | 2.6" |
| December | 25°F | 42°F | 33°F | 3.3" |
| Index | Plymouth | Pennsylvania | National |
| Air quality index | 38 | 45 | 42 |
| Pollution index | 5,949,560 | 4,584,805 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 329 |
| Days with moderate air quality | 36 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.560% |
| Benzene | 0.070% |
| Carbon Tetrachloride | 0.020% |
| Lead | 0.130% |
| Mercury | 0.040% |
| City | Population | Air Quality Index | National Avg. |
| Glen Lyon, PA | 2,929 | 38 | 24.0% |
| Larksville, PA | 4,408 | 38 | 24.0% |
| Nuangola, PA | 690 | 38 | 24.0% |
| Wanamie, PA | 603 | 38 | 24.0% |
| East Berwick, PA | 2,379 | 38 | 24.0% |
| Plymouth, PA | 5,780 | 38 | 24.0% |
| City | Population | Air Quality Index | National Avg. |
| Semmes, AL | 5,780 | 42 | 16.0% |
| Hartford City, IN | 5,781 | 35 | 30.0% |
| Lake Mohegan, NY | 5,781 | 36 | 28.0% |
| Dickson City, PA | 5,778 | 38 | 24.0% |
| Crowsnest Pass, AB | 5,778 | n/a | |
| Plymouth, PA | 5,780 | 38 | 24.0% |
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