| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 10°F | 25°F | 16°F | 3.4" |
| February | 11°F | 28°F | 19°F | 3.1" |
| March | 25°F | 44°F | 33°F | 2.2" |
| April | 39°F | 59°F | 48°F | 6.8" |
| May | 51°F | 71°F | 59°F | 4.3" |
| June | 62°F | 83°F | 71°F | 3.2" |
| July | 64°F | 85°F | 74°F | 4.7" |
| August | 61°F | 80°F | 70°F | 6.9" |
| September | 53°F | 76°F | 62°F | 5.7" |
| October | 44°F | 64°F | 52°F | 5.9" |
| November | 28°F | 46°F | 35°F | 2.9" |
| December | 9°F | 24°F | 16°F | 0.2" |
| Index | Heidelberg | Minnesota | National |
| Air quality index | 46 | 35 | 42 |
| Pollution index | 3,433,900 | 1,854,519 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 214 |
| Days with moderate air quality | 148 |
| Days w/ poor A.Q. for sensitive groups | 2 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.005% |
| Lead | 0.030% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Henderson, MN | 926 | 46 | 8.0% |
| New Prague, MN | 8,022 | 46 | 8.0% |
| Kilkenny, MN | 119 | 46 | 8.0% |
| Le Sueur, MN | 4,028 | 46 | 8.0% |
| Elko New Market, MN | 4,715 | 46 | 8.0% |
| Heidelberg, MN | 216 | 46 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Morrison Crossroads, AL | 216 | 38 | 24.0% |
| Defiance, IA | 216 | 40 | 20.0% |
| Cypress, IL | 216 | 44 | 12.0% |
| Rantoul, KS | 216 | 41 | 18.0% |
| Fountain, MI | 216 | 36 | 28.0% |
| Heidelberg, MN | 216 | 46 | 8.0% |
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