| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 9°F | 25°F | 17°F | 1.9" |
| February | 11°F | 29°F | 19°F | 1.9" |
| March | 26°F | 43°F | 34°F | 3.2" |
| April | 37°F | 59°F | 47°F | 3.3" |
| May | 48°F | 71°F | 59°F | 5.1" |
| June | 59°F | 79°F | 69°F | 7.0" |
| July | 62°F | 83°F | 72°F | 7.4" |
| August | 59°F | 80°F | 69°F | 5.1" |
| September | 53°F | 74°F | 62°F | 8.7" |
| October | 40°F | 60°F | 49°F | 3.9" |
| November | 28°F | 46°F | 36°F | 4.9" |
| December | 14°F | 29°F | 22°F | 2.9" |
| Index | Dennison | Minnesota | National |
| Air quality index | 37 | 35 | 42 |
| Pollution index | 1,803,840 | 1,854,519 | 2,726,193 |
| Measurement | Total |
| Days measured | 216 |
| Days with good air quality | 203 |
| Days with moderate air quality | 13 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.002% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.010% |
| Mercury | 0.003% |
| City | Population | Air Quality Index | National Avg. |
| Northfield, MN | 20,399 | 37 | 26.0% |
| Kenyon, MN | 1,865 | 37 | 26.0% |
| Hampton, MN | 586 | 37 | 26.0% |
| Cannon Falls, MN | 4,053 | 37 | 26.0% |
| Nerstrand, MN | 306 | 37 | 26.0% |
| Dennison, MN | 213 | 37 | 26.0% |
| City | Population | Air Quality Index | National Avg. |
| Nanwalek, AK | 213 | 31 | 38.0% |
| Sweet Water, AL | 213 | 36 | 28.0% |
| Ruth, CA | 213 | 42 | 16.0% |
| Westside, CA | 213 | 72 | 44.0% |
| Rye, CO | 213 | 20 | 60.0% |
| Dennison, MN | 213 | 37 | 26.0% |
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