| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 15°F | 34°F | 24°F | 1.5" |
| February | 16°F | 37°F | 26°F | 1.9" |
| March | 29°F | 53°F | 40°F | 2.8" |
| April | 39°F | 66°F | 52°F | 3.9" |
| May | 49°F | 76°F | 63°F | 4.3" |
| June | 60°F | 85°F | 73°F | 6.0" |
| July | 64°F | 88°F | 76°F | 5.3" |
| August | 62°F | 86°F | 73°F | 4.9" |
| September | 54°F | 81°F | 66°F | 3.4" |
| October | 42°F | 68°F | 54°F | 3.2" |
| November | 31°F | 54°F | 42°F | 2.1" |
| December | 19°F | 37°F | 28°F | 2.6" |
| Index | Geneseo | Illinois | National |
| Air quality index | 46 | 41 | 42 |
| Pollution index | 1,753,590 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 217 |
| Days with moderate air quality | 145 |
| Days w/ poor A.Q. for sensitive groups | 3 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.070% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.010% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Kewanee, IL | 12,622 | 41 | 18.0% |
| Hooppole, IL | 178 | 42 | 16.0% |
| Erie, IL | 1,865 | 42 | 16.0% |
| Hillsdale, IL | 531 | 42 | 16.0% |
| Annawan, IL | 825 | 42 | 16.0% |
| Geneseo, IL | 6,566 | 46 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| South Monrovia Island, CA | 6,565 | 72 | 44.0% |
| Westlock County, AB | 6,565 | n/a | |
| Bondurant, IA | 6,567 | 39 | 22.0% |
| Rossford, OH | 6,567 | 40 | 20.0% |
| Barrington, NS | 6,568 | n/a | |
| Geneseo, IL | 6,566 | 46 | 8.0% |
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