| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 34°F | 25°F | 3.2" |
| February | 19°F | 36°F | 27°F | 2.6" |
| March | 32°F | 51°F | 40°F | 3.2" |
| April | 41°F | 64°F | 51°F | 5.2" |
| May | 51°F | 74°F | 62°F | 5.3" |
| June | 61°F | 83°F | 71°F | 9.7" |
| July | 64°F | 86°F | 74°F | 5.3" |
| August | 62°F | 84°F | 73°F | 9.8" |
| September | 55°F | 79°F | 66°F | 6.1" |
| October | 44°F | 65°F | 54°F | 7.0" |
| November | 34°F | 52°F | 42°F | 3.8" |
| December | 24°F | 38°F | 31°F | 3.7" |
| Index | Herscher | Illinois | National |
| Air quality index | 0 | 41 | 42 |
| Pollution index | 1,736,930 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 335 |
| Days with good air quality | 334 |
| Days with moderate air quality | 1 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.004% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.001% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Bonfield, IL | 586 | 0 | 100.0% |
| Essex, IL | 1,083 | 0 | 100.0% |
| South Wilmington, IL | 702 | 0 | 100.0% |
| Buckingham, IL | 270 | 0 | 100.0% |
| Irwin, IL | 39 | 0 | 100.0% |
| Herscher, IL | 1,489 | 0 | 100.0% |
| City | Population | Air Quality Index | National Avg. |
| Ness City, KS | 1,489 | 15 | 70.0% |
| Thompson Falls, MT | 1,489 | 37 | 26.0% |
| La Huerta, NM | 1,489 | 47 | 6.0% |
| Greenwich, OH | 1,489 | 41 | 18.0% |
| New Fairview, TX | 1,489 | 51 | 2.0% |
| Herscher, IL | 1,489 | 0 | 100.0% |
Here are the best places to live in Illinois
Most Dangerous States In The US
Safest Cities In The US
Check out the 10 most dangerous cities in Illinois