| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 14°F | 28°F | 21°F | 1.7" |
| February | 16°F | 30°F | 23°F | 2.3" |
| March | 29°F | 46°F | 36°F | 2.7" |
| April | 39°F | 59°F | 48°F | 4.4" |
| May | 50°F | 71°F | 60°F | 4.6" |
| June | 60°F | 79°F | 69°F | 9.5" |
| July | 64°F | 82°F | 72°F | 7.7" |
| August | 62°F | 80°F | 71°F | 6.1" |
| September | 54°F | 74°F | 63°F | 4.2" |
| October | 43°F | 61°F | 51°F | 4.4" |
| November | 32°F | 47°F | 38°F | 3.3" |
| December | 20°F | 32°F | 26°F | 1.1" |
| Index | Janesville | Wisconsin | National |
| Air quality index | 38 | 69 | 42 |
| Pollution index | 1,129,440 | 2,842,418 | 2,726,193 |
| Measurement | Total |
| Days measured | 203 |
| Days with good air quality | 185 |
| Days with moderate air quality | 18 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.003% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.001% |
| Mercury | 0.020% |
| City | Population | Air Quality Index | National Avg. |
| Lake Koshkonong, WI | 958 | 37 | 26.0% |
| Whitewater, WI | 14,762 | 37 | 26.0% |
| Lake Lorraine, WI | 259 | 37 | 26.0% |
| South Beloit, IL | 7,730 | 38 | 24.0% |
| Orfordville, WI | 1,450 | 38 | 24.0% |
| Janesville, WI | 64,415 | 38 | 24.0% |
| City | Population | Air Quality Index | National Avg. |
| Noblesville, IN | 64,430 | 42 | 16.0% |
| Castro Valley, CA | 64,392 | 40 | 20.0% |
| Eden Prairie, MN | 64,481 | 46 | 8.0% |
| Port Charlotte, FL | 64,335 | 36 | 28.0% |
| Tulare, CA | 64,546 | 66 | 32.0% |
| Janesville, WI | 64,415 | 38 | 24.0% |
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