| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 6°F | 25°F | 15°F | 0.6" |
| February | 7°F | 26°F | 16°F | 1.3" |
| March | 22°F | 41°F | 30°F | 1.2" |
| April | 34°F | 57°F | 44°F | 2.5" |
| May | 46°F | 71°F | 57°F | 2.5" |
| June | 57°F | 80°F | 68°F | 4.1" |
| July | 61°F | 85°F | 72°F | 2.6" |
| August | 58°F | 81°F | 69°F | 3.2" |
| September | 50°F | 75°F | 61°F | 2.7" |
| October | 38°F | 60°F | 47°F | 2.7" |
| November | 24°F | 45°F | 33°F | 0.5" |
| December | 9°F | 27°F | 18°F | 1.0" |
| Index | Ortonville | Minnesota | National |
| Air quality index | 25 | 35 | 42 |
| Pollution index | 358,608 | 1,854,519 | 2,726,193 |
| Measurement | Total |
| Days measured | 361 |
| Days with good air quality | 325 |
| Days with moderate air quality | 36 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.002% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Clinton, MN | 320 | 25 | 50.0% |
| Big Stone City, SD | 681 | 25 | 50.0% |
| Correll, MN | 49 | 25 | 50.0% |
| Milbank, SD | 3,218 | 25 | 50.0% |
| Louisburg, MN | 29 | 25 | 50.0% |
| Ortonville, MN | 2,090 | 25 | 50.0% |
| City | Population | Air Quality Index | National Avg. |
| Marceline, MO | 2,090 | 38 | 24.0% |
| Pahala, HI | 2,089 | 16 | 68.0% |
| Prairie Grove, IL | 2,089 | 39 | 22.0% |
| Grove Hill, AL | 2,088 | 36 | 28.0% |
| Fort Denaud, FL | 2,088 | 36 | 28.0% |
| Ortonville, MN | 2,090 | 25 | 50.0% |