| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 20°F | 38°F | 29°F | 2.1" |
| February | 22°F | 41°F | 31°F | 1.9" |
| March | 34°F | 56°F | 44°F | 2.9" |
| April | 44°F | 68°F | 56°F | 4.3" |
| May | 54°F | 77°F | 65°F | 4.5" |
| June | 64°F | 86°F | 74°F | 5.5" |
| July | 66°F | 88°F | 77°F | 4.3" |
| August | 64°F | 86°F | 75°F | 3.2" |
| September | 57°F | 81°F | 68°F | 3.7" |
| October | 46°F | 69°F | 56°F | 3.7" |
| November | 36°F | 55°F | 45°F | 2.5" |
| December | 26°F | 41°F | 33°F | 2.8" |
| Index | Rochester | Illinois | National |
| Air quality index | 40 | 41 | 42 |
| Pollution index | 5,136,080 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 360 |
| Days with good air quality | 287 |
| Days with moderate air quality | 73 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.090% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.390% |
| Mercury | 0.020% |
| City | Population | Air Quality Index | National Avg. |
| Bulpitt, IL | 236 | 40 | 20.0% |
| Divernon, IL | 1,194 | 40 | 20.0% |
| Jerome, IL | 1,973 | 40 | 20.0% |
| Pawnee, IL | 2,522 | 40 | 20.0% |
| Langleyville, IL | 439 | 40 | 20.0% |
| Rochester, IL | 3,778 | 40 | 20.0% |
| City | Population | Air Quality Index | National Avg. |
| Alturas, FL | 3,778 | 36 | 28.0% |
| Independence, MN | 3,778 | 46 | 8.0% |
| Hardin, MT | 3,777 | 21 | 58.0% |
| Tiffin, IA | 3,779 | 35 | 30.0% |
| Bayshore, NC | 3,776 | 34 | 32.0% |
| Rochester, IL | 3,778 | 40 | 20.0% |
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