| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 13°F | 31°F | 21°F | 2.9" |
| February | 15°F | 33°F | 23°F | 2.6" |
| March | 29°F | 49°F | 38°F | 4.2" |
| April | 39°F | 62°F | 50°F | 6.5" |
| May | 51°F | 74°F | 61°F | 6.2" |
| June | 61°F | 82°F | 71°F | 7.9" |
| July | 64°F | 84°F | 73°F | 6.6" |
| August | 61°F | 82°F | 71°F | 9.8" |
| September | 53°F | 76°F | 64°F | 6.2" |
| October | 42°F | 64°F | 52°F | 6.1" |
| November | 30°F | 50°F | 39°F | 4.3" |
| December | 19°F | 34°F | 26°F | 4.0" |
| Index | Hillsdale | Illinois | National |
| Air quality index | 42 | 41 | 42 |
| Pollution index | 1,753,590 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 268 |
| Days with moderate air quality | 96 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.070% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.010% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Atkinson, IL | 1,335 | 42 | 16.0% |
| Camanche, IA | 4,342 | 42 | 16.0% |
| Cordova, IL | 685 | 42 | 16.0% |
| Prophetstown, IL | 1,965 | 42 | 16.0% |
| Low Moor, IA | 326 | 42 | 16.0% |
| Hillsdale, IL | 531 | 42 | 16.0% |
| City | Population | Air Quality Index | National Avg. |
| Central City, CO | 531 | 47 | 6.0% |
| University Park, IA | 531 | 39 | 22.0% |
| Pretty Prairie, KS | 531 | 40 | 20.0% |
| Hartland, ME | 531 | 31 | 38.0% |
| Ottertail, MN | 531 | 29 | 42.0% |
| Hillsdale, IL | 531 | 42 | 16.0% |
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