| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 25°F | 41°F | 32°F | 5.0" |
| February | 26°F | 43°F | 34°F | 3.4" |
| March | 38°F | 58°F | 47°F | 4.9" |
| April | 47°F | 69°F | 57°F | 9.7" |
| May | 57°F | 77°F | 66°F | 7.4" |
| June | 66°F | 87°F | 76°F | 8.6" |
| July | 68°F | 89°F | 78°F | 6.6" |
| August | 66°F | 88°F | 76°F | 8.7" |
| September | 58°F | 81°F | 68°F | 7.6" |
| October | 47°F | 70°F | 58°F | 7.1" |
| November | 37°F | 57°F | 46°F | 6.0" |
| December | 30°F | 45°F | 36°F | 6.6" |
| Index | Carlyle | 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. |
| Keyesport, IL | 493 | 43 | 14.0% |
| Beckemeyer, IL | 1,054 | 43 | 14.0% |
| Germantown, IL | 1,279 | 43 | 14.0% |
| Sandoval, IL | 1,099 | 43 | 14.0% |
| Okawville, IL | 1,469 | 43 | 14.0% |
| Carlyle, IL | 3,595 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Hainesville, IL | 3,595 | 39 | 22.0% |
| East Angus, QC | 3,595 | n/a | |
| Boonsboro, MD | 3,594 | 40 | 20.0% |
| O'Neill, NE | 3,594 | 19 | 62.0% |
| Blanding, UT | 3,594 | 44 | 12.0% |
| Carlyle, IL | 3,595 | 43 | 14.0% |
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