| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 35°F | 28°F | 4.7" |
| February | 20°F | 34°F | 26°F | 2.5" |
| March | 33°F | 54°F | 42°F | 4.9" |
| April | 42°F | 65°F | 52°F | 4.6" |
| May | 53°F | 77°F | 65°F | 3.7" |
| June | 64°F | 86°F | 74°F | 4.4" |
| July | 65°F | 86°F | 75°F | 4.9" |
| August | 66°F | 88°F | 76°F | 3.8" |
| September | 59°F | 85°F | 70°F | 4.4" |
| October | 48°F | 70°F | 57°F | 5.3" |
| November | 34°F | 53°F | 42°F | 5.3" |
| December | 20°F | 33°F | 26°F | 2.9" |
| Index | Heyworth | Illinois | National |
| Air quality index | 44 | 41 | 50 |
| Pollution index | 607,262 | 3,347,295 | 5,066,862 |
| 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, State | Population | Air Quality Index | National Avg. |
| Wapella, IL | 557 | 44 | 12% |
| Ellsworth, IL | 276 | 44 | 12% |
| Beason, IL | 70 | 44 | 12% |
| Danvers, IL | 1,291 | 44 | 12% |
| Waynesville, IL | 463 | 44 | 12% |
| Heyworth, IL | 3,031 | 44 | 12% |
| City, State | Population | Air Quality Index | National Avg. |
| San Saba, TX | 3,030 | 42 | 16% |
| Bellows Falls, VT | 3,032 | 34 | 32% |
| Travis Ranch, TX | 3,032 | 51 | 2% |
| Verona, MS | 3,032 | 39 | 22% |
| Rose Hills, CA | 3,033 | 72 | 44% |
| Heyworth, IL | 3,031 | 44 | 12% |
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