| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 23°F | 38°F | 29°F | 3.3" |
| February | 24°F | 40°F | 31°F | 3.5" |
| March | 36°F | 55°F | 44°F | 3.9" |
| April | 45°F | 67°F | 55°F | 9.3" |
| May | 55°F | 75°F | 64°F | 5.6" |
| June | 64°F | 84°F | 73°F | 7.9" |
| July | 66°F | 86°F | 76°F | 5.0" |
| August | 65°F | 86°F | 74°F | 5.1" |
| September | 57°F | 80°F | 67°F | 6.0" |
| October | 46°F | 68°F | 56°F | 5.6" |
| November | 36°F | 54°F | 44°F | 3.6" |
| December | 28°F | 42°F | 34°F | 3.6" |
| Index | Greenville | Illinois | National |
| Air quality index | 43 | 41 | 42 |
| Pollution index | 647,280 | 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. |
| Mulberry Grove, IL | 847 | 40 | 20.0% |
| Coffeen, IL | 640 | 40 | 20.0% |
| Smithboro, IL | 215 | 40 | 20.0% |
| Keyesport, IL | 493 | 43 | 14.0% |
| Sorento, IL | 499 | 54 | 8.0% |
| Greenville, IL | 6,725 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Gulf Breeze, FL | 6,725 | 41 | 18.0% |
| Manorhaven, NY | 6,725 | 51 | 2.0% |
| Demopolis, AL | 6,724 | 36 | 28.0% |
| Tallulah, LA | 6,722 | 34 | 32.0% |
| Minden Hills, ON | 6,722 | n/a | |
| Greenville, IL | 6,725 | 43 | 14.0% |
Here are the best places to live in Illinois
Most Dangerous Cities In The US
Check out the 10 safest cities in Illinois
See the best places to live in Greenville