| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 13°F | 28°F | 21°F | 3.6" |
| February | 14°F | 30°F | 22°F | 1.7" |
| March | 26°F | 45°F | 35°F | 3.4" |
| April | 37°F | 59°F | 47°F | 6.3" |
| May | 47°F | 71°F | 59°F | 5.1" |
| June | 57°F | 79°F | 68°F | 7.3" |
| July | 61°F | 83°F | 72°F | 3.8" |
| August | 59°F | 81°F | 70°F | 5.7" |
| September | 51°F | 74°F | 62°F | 4.6" |
| October | 41°F | 61°F | 50°F | 6.5" |
| November | 30°F | 47°F | 38°F | 4.2" |
| December | 18°F | 33°F | 25°F | 3.3" |
| Index | Jefferson | Wisconsin | National |
| Air quality index | 37 | 69 | 42 |
| Pollution index | 2,796,310 | 2,842,418 | 2,726,193 |
| Measurement | Total |
| Days measured | 205 |
| Days with good air quality | 189 |
| Days with moderate air quality | 15 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.003% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.005% |
| Lead | 0.001% |
| Mercury | 0.004% |
| City | Population | Air Quality Index | National Avg. |
| Lake Mills, WI | 5,936 | 37 | 26.0% |
| Waterloo, WI | 3,334 | 37 | 26.0% |
| Johnson Creek, WI | 3,029 | 37 | 26.0% |
| Sullivan, WI | 710 | 37 | 26.0% |
| Ashippun, WI | 1,027 | 37 | 26.0% |
| Jefferson, WI | 8,011 | 37 | 26.0% |
| City | Population | Air Quality Index | National Avg. |
| Whitmore Lake, MI | 8,010 | 40 | 20.0% |
| Downingtown, PA | 8,012 | 42 | 16.0% |
| Stone Mills, ON | 8,012 | n/a | |
| Rockwood, VA | 8,008 | 44 | 12.0% |
| Vermilion River County, AB | 8,008 | n/a | |
| Jefferson, WI | 8,011 | 37 | 26.0% |
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