| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 9°F | 29°F | 19°F | 1.3" |
| February | 11°F | 33°F | 22°F | 1.2" |
| March | 25°F | 49°F | 36°F | 1.9" |
| April | 36°F | 63°F | 49°F | 5.0" |
| May | 47°F | 74°F | 60°F | 4.8" |
| June | 58°F | 83°F | 71°F | 6.5" |
| July | 61°F | 86°F | 74°F | 4.9" |
| August | 58°F | 84°F | 71°F | 4.0" |
| September | 51°F | 79°F | 64°F | 3.4" |
| October | 39°F | 65°F | 51°F | 3.2" |
| November | 27°F | 50°F | 38°F | 1.8" |
| December | 14°F | 33°F | 23°F | 2.1" |
| Index | Janesville | Iowa | National |
| Air quality index | 39 | 39 | 42 |
| Pollution index | 1,013,960 | 1,154,535 | 2,726,193 |
| Measurement | Total |
| Days measured | 363 |
| Days with good air quality | 286 |
| Days with moderate air quality | 77 |
| 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 | 0.001% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Readlyn, IA | 804 | 39 | 22.0% |
| Dike, IA | 1,192 | 39 | 22.0% |
| Stout, IA | 214 | 39 | 22.0% |
| Plainfield, IA | 405 | 39 | 22.0% |
| Raymond, IA | 792 | 39 | 22.0% |
| Janesville, IA | 1,051 | 39 | 22.0% |
| City | Population | Air Quality Index | National Avg. |
| Mineral Springs, AR | 1,051 | 39 | 22.0% |
| Alhambra Valley, CA | 1,051 | 40 | 20.0% |
| Hydesville, CA | 1,051 | 27 | 46.0% |
| Argenta, IL | 1,051 | 44 | 12.0% |
| Ashley, IN | 1,051 | 45 | 10.0% |
| Janesville, IA | 1,051 | 39 | 22.0% |
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