| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 34°F | 25°F | 3.2" |
| February | 19°F | 36°F | 27°F | 3.2" |
| March | 32°F | 51°F | 41°F | 5.1" |
| April | 42°F | 64°F | 52°F | 6.5" |
| May | 53°F | 74°F | 63°F | 7.0" |
| June | 62°F | 82°F | 72°F | 7.0" |
| July | 65°F | 85°F | 74°F | 7.2" |
| August | 64°F | 84°F | 73°F | 8.3" |
| September | 57°F | 78°F | 66°F | 7.1" |
| October | 45°F | 65°F | 54°F | 6.0" |
| November | 34°F | 52°F | 42°F | 4.6" |
| December | 23°F | 38°F | 30°F | 3.8" |
| Index | Lacon | Illinois | National |
| Air quality index | 41 | 41 | 42 |
| Pollution index | 339,156 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 285 |
| Days with moderate air quality | 78 |
| Days w/ poor A.Q. for sensitive groups | 2 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| McNabb, IL | 237 | 0 | 100.0% |
| Toluca, IL | 1,287 | 0 | 100.0% |
| Magnolia, IL | 263 | 0 | 100.0% |
| Henry, IL | 2,352 | 41 | 18.0% |
| La Rose, IL | 114 | 41 | 18.0% |
| Lacon, IL | 1,771 | 41 | 18.0% |
| City | Population | Air Quality Index | National Avg. |
| Crothersville, IN | 1,771 | 35 | 30.0% |
| Adwolf, VA | 1,771 | 26 | 48.0% |
| Fort Deposit, AL | 1,770 | 52 | 4.0% |
| Stamps, AR | 1,770 | 39 | 22.0% |
| Jonesboro, IL | 1,772 | 44 | 12.0% |
| Lacon, IL | 1,771 | 41 | 18.0% |
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