| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 39°F | 30°F | 3.1" |
| February | 23°F | 43°F | 32°F | 2.8" |
| March | 31°F | 53°F | 41°F | 4.3" |
| April | 42°F | 66°F | 54°F | 4.0" |
| May | 53°F | 76°F | 64°F | 4.5" |
| June | 62°F | 83°F | 73°F | 5.2" |
| July | 68°F | 88°F | 78°F | 5.2" |
| August | 65°F | 85°F | 74°F | 4.5" |
| September | 59°F | 80°F | 68°F | 5.7" |
| October | 47°F | 68°F | 57°F | 5.2" |
| November | 34°F | 55°F | 44°F | 2.4" |
| December | 29°F | 45°F | 37°F | 3.4" |
| Index | Royalton | Pennsylvania | National |
| Air quality index | 44 | 45 | 42 |
| Pollution index | 11,091,200 | 4,584,805 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 252 |
| Days with moderate air quality | 107 |
| Days w/ poor A.Q. for sensitive groups | 5 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.140% |
| Carbon Tetrachloride | 0.030% |
| Lead | 0.310% |
| Mercury | 0.004% |
| City | Population | Air Quality Index | National Avg. |
| East Prospect, PA | 756 | 41 | 18.0% |
| Marietta, PA | 2,616 | 41 | 18.0% |
| Weigelstown, PA | 14,156 | 41 | 18.0% |
| Falmouth, PA | 569 | 41 | 18.0% |
| Manchester, PA | 2,680 | 41 | 18.0% |
| Royalton, PA | 1,149 | 44 | 12.0% |
| City | Population | Air Quality Index | National Avg. |
| Minturn, CO | 1,149 | 47 | 6.0% |
| Palm Beach Shores, FL | 1,149 | 36 | 28.0% |
| Wayland, IA | 1,149 | 35 | 30.0% |
| New Pekin, IN | 1,149 | 49 | 2.0% |
| Wellsville, MO | 1,149 | 38 | 24.0% |
| Royalton, PA | 1,149 | 44 | 12.0% |
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