| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 24°F | 41°F | 31°F | 3.4" |
| February | 25°F | 43°F | 33°F | 3.7" |
| March | 38°F | 57°F | 46°F | 3.1" |
| April | 47°F | 68°F | 56°F | 6.6" |
| May | 56°F | 76°F | 65°F | 6.1" |
| June | 65°F | 85°F | 75°F | 3.5" |
| July | 67°F | 87°F | 77°F | 7.3" |
| August | 66°F | 86°F | 75°F | 6.8" |
| September | 58°F | 80°F | 68°F | 4.4" |
| October | 47°F | 68°F | 57°F | 6.7" |
| November | 36°F | 56°F | 45°F | 4.9" |
| December | 28°F | 43°F | 35°F | 6.3" |
| Index | Mitchell | Illinois | National |
| Air quality index | 54 | 41 | 50 |
| Pollution index | 8,473,050 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 134 |
| Days with moderate air quality | 221 |
| Days w/ poor A.Q. for sensitive groups | 8 |
| Days with unhealthy air quality | 2 |
| Pollutant | Total |
| Arsenic | 0.020% |
| Benzene | 0.070% |
| Carbon Tetrachloride | 0.020% |
| Lead | 0.010% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Godfrey, IL | 17,809 | 54 | 8.0% |
| Florissant, MO | 52,218 | 54 | 8.0% |
| East Alton, IL | 6,171 | 54 | 8.0% |
| Hartford, IL | 1,569 | 54 | 8.0% |
| South Roxana, IL | 2,316 | 54 | 8.0% |
| Mitchell, IL | 1,183 | 54 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Johnstonville, CA | 1,183 | 46 | 8.0% |
| Gilbert, IA | 1,183 | 37 | 26.0% |
| Alma, NE | 1,183 | 19 | 62.0% |
| Dover Beaches South, NJ | 1,183 | 41 | 18.0% |
| Pandora, OH | 1,183 | 39 | 22.0% |
| Mitchell, IL | 1,183 | 54 | 8.0% |
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