| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 34°F | 26°F | 3.3" |
| February | 19°F | 35°F | 26°F | 3.0" |
| March | 32°F | 51°F | 40°F | 4.3" |
| April | 42°F | 64°F | 52°F | 7.2" |
| May | 53°F | 75°F | 63°F | 8.0" |
| June | 62°F | 83°F | 72°F | 7.5" |
| July | 66°F | 85°F | 75°F | 7.1" |
| August | 64°F | 83°F | 73°F | 8.2" |
| September | 56°F | 78°F | 66°F | 6.3" |
| October | 45°F | 65°F | 54°F | 6.6" |
| November | 34°F | 51°F | 42°F | 4.3" |
| December | 23°F | 37°F | 30°F | 3.5" |
| Index | Dayton | Illinois | National |
| Air quality index | 0 | 41 | 50 |
| Pollution index | 1,874,490 | 3,347,295 | 5,066,862 |
| 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 | 0.002% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.010% |
| Mercury | 0.010% |
| City, State | Population | Air Quality Index | National Avg. |
| Earlville, IL | 1,672 | 0 | 100% |
| North Utica, IL | 1,402 | 0 | 100% |
| Leonore, IL | 90 | 0 | 100% |
| Seneca, IL | 2,565 | 0 | 100% |
| Newark, IL | 1,139 | 0 | 100% |
| Dayton, IL | 520 | 0 | 100% |
| City, State | Population | Air Quality Index | National Avg. |
| Plantation Island, FL | 520 | 34 | 32% |
| Troutville, VA | 520 | 38 | 24% |
| Peterstown, WV | 520 | 41 | 18% |
| Rocky Ridge, OH | 520 | 40 | 20% |
| Sidell, IL | 520 | 42 | 16% |
| Dayton, IL | 520 | 0 | 100% |
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