| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 27°F | 43°F | 34°F | 5.0" |
| February | 28°F | 46°F | 36°F | 4.8" |
| March | 39°F | 59°F | 48°F | 4.5" |
| April | 48°F | 70°F | 58°F | 10.6" |
| May | 57°F | 78°F | 67°F | 6.0" |
| June | 66°F | 87°F | 76°F | 7.6" |
| July | 67°F | 88°F | 77°F | 6.8" |
| August | 65°F | 87°F | 76°F | 5.4" |
| September | 58°F | 82°F | 69°F | 6.5" |
| October | 47°F | 71°F | 58°F | 3.5" |
| November | 37°F | 58°F | 47°F | 6.2" |
| December | 31°F | 47°F | 38°F | 8.9" |
| Index | Old Shawneetown | Illinois | National |
| Air quality index | 45 | 41 | 50 |
| Pollution index | 768,150 | 3,347,295 | 5,066,862 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 244 |
| Days with moderate air quality | 111 |
| Days w/ poor A.Q. for sensitive groups | 10 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.005% |
| Lead | 0.003% |
| Mercury | 0.000% |
| City, State | Population | Air Quality Index | National Avg. |
| Junction, IL | 114 | 45 | 10% |
| Morganfield, KY | 3,571 | 45 | 10% |
| New Haven, IL | 382 | 45 | 10% |
| Shawneetown, IL | 1,340 | 45 | 10% |
| Sturgis, KY | 1,904 | 45 | 10% |
| Old Shawneetown, IL | 130 | 45 | 10% |
| City, State | Population | Air Quality Index | National Avg. |
| Rockville, MO | 130 | 37 | 26% |
| Godwin, NC | 130 | 41 | 18% |
| Montpelier, ND | 130 | 33 | 34% |
| Lequire, OK | 130 | 43 | 14% |
| Westphalia, IA | 130 | 40 | 20% |
| Old Shawneetown, IL | 130 | 45 | 10% |
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