| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 10°F | 33°F | 21°F | 0.7" |
| February | 13°F | 38°F | 24°F | 0.8" |
| March | 26°F | 53°F | 38°F | 1.5" |
| April | 37°F | 66°F | 51°F | 3.5" |
| May | 48°F | 77°F | 62°F | 4.2" |
| June | 59°F | 86°F | 72°F | 4.9" |
| July | 63°F | 89°F | 76°F | 3.5" |
| August | 60°F | 86°F | 73°F | 5.6" |
| September | 51°F | 81°F | 65°F | 3.1" |
| October | 38°F | 68°F | 52°F | 3.0" |
| November | 25°F | 53°F | 38°F | 1.1" |
| December | 13°F | 36°F | 24°F | 1.7" |
| Index | Jefferson | South Dakota | National |
| Air quality index | 35 | 36 | 42 |
| Pollution index | 397,267 | 345,623 | 2,726,193 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 322 |
| Days with moderate air quality | 42 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Sioux City, IA | 82,535 | 35 | 30.0% |
| South Sioux City, NE | 12,867 | 35 | 30.0% |
| Allen, NE | 405 | 35 | 30.0% |
| Westfield, IA | 120 | 35 | 30.0% |
| Dakota City, NE | 2,249 | 35 | 30.0% |
| Jefferson, SD | 677 | 35 | 30.0% |
| City | Population | Air Quality Index | National Avg. |
| Butte Creek Canyon, CA | 677 | 46 | 8.0% |
| Pippa Passes, KY | 677 | 45 | 10.0% |
| Highland Holiday, OH | 677 | 47 | 6.0% |
| Zavalla, TX | 677 | 45 | 10.0% |
| Albion, WA | 677 | 18 | 64.0% |
| Jefferson, SD | 677 | 35 | 30.0% |
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