| 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 | Milan | Illinois | National |
| Air quality index | 46 | 41 | 42 |
| Pollution index | 4,003,130 | 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 | 0.170% |
| Benzene | 0.050% |
| Carbon Tetrachloride | 0.110% |
| Lead | 0.020% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Carbon Cliff, IL | 1,937 | 46 | 8.0% |
| Moline, IL | 41,213 | 46 | 8.0% |
| Reynolds, IL | 680 | 46 | 8.0% |
| Oak Grove, IL | 427 | 46 | 8.0% |
| Walcott, IA | 1,802 | 46 | 8.0% |
| Milan, IL | 5,001 | 46 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Annville, PA | 5,001 | 42 | 16.0% |
| Post, TX | 5,002 | 25 | 50.0% |
| Paulden, AZ | 5,003 | 43 | 14.0% |
| Metchosin, BC | 4,998 | n/a | |
| Richland Center, WI | 4,997 | 35 | 30.0% |
| Milan, IL | 5,001 | 46 | 8.0% |
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