| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 6°F | 24°F | 15°F | 1.9" |
| February | 3°F | 25°F | 14°F | 2.5" |
| March | 19°F | 41°F | 29°F | 1.9" |
| April | 31°F | 56°F | 43°F | 3.9" |
| May | 42°F | 67°F | 55°F | 4.9" |
| June | 54°F | 78°F | 66°F | 4.9" |
| July | 58°F | 81°F | 70°F | 8.9" |
| August | 56°F | 78°F | 67°F | 8.7" |
| September | 50°F | 73°F | 61°F | 5.1" |
| October | 36°F | 58°F | 47°F | 3.9" |
| November | 24°F | 43°F | 32°F | 3.8" |
| December | 12°F | 27°F | 20°F | 1.4" |
| Index | Royalton | Minnesota | National |
| Air quality index | 32 | 35 | 42 |
| Pollution index | 1,174,010 | 1,854,519 | 2,726,193 |
| Measurement | Total |
| Days measured | 344 |
| Days with good air quality | 313 |
| Days with moderate air quality | 31 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.002% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.001% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Genola, MN | 84 | 29 | 42.0% |
| Flensburg, MN | 218 | 29 | 42.0% |
| Lastrup, MN | 146 | 29 | 42.0% |
| Little Falls, MN | 8,663 | 29 | 42.0% |
| Pierz, MN | 1,573 | 29 | 42.0% |
| Royalton, MN | 1,186 | 32 | 36.0% |
| City | Population | Air Quality Index | National Avg. |
| Sand Point, AK | 1,186 | 31 | 38.0% |
| Roseland, LA | 1,186 | 30 | 40.0% |
| Boley, OK | 1,186 | 36 | 28.0% |
| North Apollo, PA | 1,186 | 38 | 24.0% |
| Wayne, WV | 1,186 | 42 | 16.0% |
| Royalton, MN | 1,186 | 32 | 36.0% |
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