| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 25°F | 42°F | 33°F | 4.6" |
| February | 27°F | 45°F | 35°F | 2.4" |
| March | 39°F | 58°F | 48°F | 3.7" |
| April | 48°F | 69°F | 58°F | 6.6" |
| May | 57°F | 77°F | 66°F | 10.0" |
| June | 66°F | 86°F | 76°F | 8.8" |
| July | 69°F | 88°F | 78°F | 6.8" |
| August | 67°F | 87°F | 76°F | 10.7" |
| September | 59°F | 81°F | 69°F | 7.4" |
| October | 48°F | 70°F | 58°F | 9.0" |
| November | 38°F | 57°F | 47°F | 6.5" |
| December | 30°F | 45°F | 37°F | 7.7" |
| Index | Rockwood | Illinois | National |
| Air quality index | 43 | 41 | 42 |
| Pollution index | 753,473 | 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 | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.020% |
| Mercury | 0.020% |
| City | Population | Air Quality Index | National Avg. |
| Willisville, IL | 596 | 43 | 14.0% |
| Grand Tower, IL | 589 | 43 | 14.0% |
| Ava, IL | 541 | 43 | 14.0% |
| Cutler, IL | 429 | 43 | 14.0% |
| Altenburg, MO | 345 | 43 | 14.0% |
| Rockwood, IL | 25 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Mendeltna, AK | 25 | 31 | 38.0% |
| Beyerville, AZ | 25 | 31 | 38.0% |
| Butte Meadows, CA | 25 | 46 | 8.0% |
| Lazy Lake, FL | 25 | 41 | 18.0% |
| Blanchard, IA | 25 | 43 | 14.0% |
| Rockwood, IL | 25 | 43 | 14.0% |
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