| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 28°F | 43°F | 34°F | 9.8" |
| February | 26°F | 45°F | 34°F | 4.7" |
| March | 38°F | 60°F | 48°F | 2.9" |
| April | 45°F | 68°F | 56°F | 5.6" |
| May | 56°F | 79°F | 67°F | 3.7" |
| June | 65°F | 88°F | 76°F | 7.6" |
| July | 67°F | 88°F | 77°F | 12.3" |
| August | 70°F | 93°F | 80°F | 7.2" |
| September | 61°F | 85°F | 72°F | 16.1" |
| October | 49°F | 72°F | 59°F | 7.5" |
| November | 38°F | 59°F | 47°F | 11.9" |
| December | 27°F | 42°F | 33°F | 2.9" |
| Index | Okawville | Illinois | National |
| Air quality index | 43 | 41 | 42 |
| Pollution index | 569,178 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 344 |
| Days with good air quality | 269 |
| Days with moderate air quality | 74 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Breese, IL | 4,160 | 43 | 14.0% |
| Hoyleton, IL | 507 | 43 | 14.0% |
| Oakdale, IL | 291 | 43 | 14.0% |
| New Minden, IL | 185 | 43 | 14.0% |
| Addieville, IL | 386 | 43 | 14.0% |
| Okawville, IL | 1,469 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Cohoe, AK | 1,469 | 31 | 38.0% |
| Holly Hill, SC | 1,469 | 29 | 42.0% |
| Danbury, TX | 1,469 | 52 | 4.0% |
| Clarendon, AR | 1,470 | 45 | 10.0% |
| Brooklet, GA | 1,470 | 39 | 22.0% |
| Okawville, IL | 1,469 | 43 | 14.0% |
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