| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 35°F | 26°F | 2.3" |
| February | 19°F | 36°F | 27°F | 1.8" |
| March | 32°F | 52°F | 41°F | 3.1" |
| April | 42°F | 65°F | 53°F | 4.7" |
| May | 53°F | 75°F | 63°F | 5.5" |
| June | 63°F | 83°F | 73°F | 4.4" |
| July | 65°F | 85°F | 75°F | 4.7" |
| August | 63°F | 84°F | 73°F | 4.4" |
| September | 56°F | 79°F | 66°F | 4.9" |
| October | 45°F | 66°F | 54°F | 4.7" |
| November | 33°F | 52°F | 42°F | 3.2" |
| December | 23°F | 38°F | 30°F | 3.1" |
| Index | Congerville | Illinois | National |
| Air quality index | 44 | 41 | 42 |
| Pollution index | 607,262 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 256 |
| Days with moderate air quality | 108 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Metamora, IL | 3,840 | 41 | 18.0% |
| Mackinaw, IL | 1,970 | 41 | 18.0% |
| Washington, IL | 16,555 | 41 | 18.0% |
| Morton, IL | 15,791 | 41 | 18.0% |
| Roanoke, IL | 1,880 | 41 | 18.0% |
| Congerville, IL | 840 | 44 | 12.0% |
| City | Population | Air Quality Index | National Avg. |
| Cedar Key, FL | 840 | 30 | 40.0% |
| Pendergrass, GA | 840 | 37 | 26.0% |
| Garrett Park, MD | 840 | 47 | 6.0% |
| Inverness, MS | 840 | 43 | 14.0% |
| Attica, OH | 840 | 41 | 18.0% |
| Congerville, IL | 840 | 44 | 12.0% |
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