| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 9°F | 24°F | 16°F | 0.3" |
| February | 11°F | 27°F | 18°F | 0.3" |
| March | 26°F | 42°F | 33°F | 1.2" |
| April | 38°F | 58°F | 46°F | 2.8" |
| May | 49°F | 70°F | 59°F | 2.7" |
| June | 59°F | 79°F | 68°F | 5.8" |
| July | 63°F | 83°F | 72°F | 4.9" |
| August | 60°F | 80°F | 69°F | 3.2" |
| September | 52°F | 74°F | 62°F | 3.4" |
| October | 41°F | 59°F | 49°F | 2.0" |
| November | 28°F | 45°F | 36°F | 0.6" |
| December | 15°F | 28°F | 21°F | 0.6" |
| Index | Waltham | Minnesota | National |
| Air quality index | 36 | 35 | 42 |
| Pollution index | 1,320,050 | 1,854,519 | 2,726,193 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 313 |
| Days with moderate air quality | 51 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.010% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Mapleview, MN | 142 | 36 | 28.0% |
| Dodge Center, MN | 2,750 | 36 | 28.0% |
| Dexter, MN | 338 | 36 | 28.0% |
| Rose Creek, MN | 536 | 36 | 28.0% |
| Hayfield, MN | 1,299 | 36 | 28.0% |
| Waltham, MN | 168 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Marshall, AK | 168 | 31 | 38.0% |
| Sedgwick, AR | 168 | 45 | 10.0% |
| Elgin, AZ | 168 | 45 | 10.0% |
| La Junta Gardens, CO | 168 | 20 | 60.0% |
| Makena, HI | 168 | 15 | 70.0% |
| Waltham, MN | 168 | 36 | 28.0% |
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