| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 30°F | 44°F | 36°F | 7.5" |
| February | 28°F | 46°F | 36°F | 4.9" |
| March | 38°F | 61°F | 49°F | 4.2" |
| April | 45°F | 67°F | 56°F | 5.8" |
| May | 55°F | 79°F | 67°F | 4.4" |
| June | 65°F | 87°F | 76°F | 5.4" |
| July | 66°F | 87°F | 76°F | 3.6" |
| August | 69°F | 92°F | 80°F | 3.8" |
| September | 60°F | 85°F | 71°F | 5.0" |
| October | 48°F | 73°F | 59°F | 5.5" |
| November | 38°F | 59°F | 48°F | 11.1" |
| December | 28°F | 45°F | 36°F | 6.7" |
| Index | Jonesboro | Illinois | National |
| Air quality index | 44 | 41 | 42 |
| Pollution index | 2,331,220 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 261 |
| Days with moderate air quality | 103 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.004% |
| Lead | 0.002% |
| Mercury | 0.260% |
| City | Population | Air Quality Index | National Avg. |
| Grand Tower, IL | 589 | 43 | 14.0% |
| Anna, IL | 4,149 | 44 | 12.0% |
| Makanda, IL | 541 | 44 | 12.0% |
| Cypress, IL | 216 | 44 | 12.0% |
| Cape Girardeau, MO | 40,100 | 44 | 12.0% |
| Jonesboro, IL | 1,772 | 44 | 12.0% |
| City | Population | Air Quality Index | National Avg. |
| Montour Falls, NY | 1,772 | 35 | 30.0% |
| Kiawah Island, SC | 1,772 | 38 | 24.0% |
| Lyndhurst, VA | 1,772 | 40 | 20.0% |
| Lacon, IL | 1,771 | 41 | 18.0% |
| Crothersville, IN | 1,771 | 35 | 30.0% |
| Jonesboro, IL | 1,772 | 44 | 12.0% |
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