| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 33°F | 25°F | 4.0" |
| February | 13°F | 30°F | 22°F | 3.3" |
| March | 25°F | 45°F | 35°F | 3.0" |
| April | 35°F | 60°F | 48°F | 2.7" |
| May | 43°F | 71°F | 57°F | 3.9" |
| June | 55°F | 83°F | 70°F | 5.1" |
| July | 56°F | 83°F | 71°F | 4.4" |
| August | 59°F | 83°F | 71°F | 3.9" |
| September | 49°F | 78°F | 63°F | 1.9" |
| October | 42°F | 66°F | 54°F | 2.3" |
| November | 28°F | 49°F | 39°F | 5.0" |
| December | 19°F | 32°F | 26°F | 3.5" |
| Index | Knollwood | Illinois | National |
| Air quality index | 39 | 41 | 42 |
| Pollution index | 543,516 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 203 |
| Days with good air quality | 174 |
| Days with moderate air quality | 28 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.004% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Lindenhurst, IL | 14,317 | 39 | 22.0% |
| Gurnee, IL | 30,519 | 39 | 22.0% |
| Long Lake, IL | 3,065 | 39 | 22.0% |
| Green Oaks, IL | 3,882 | 39 | 22.0% |
| Channel Lake, IL | 1,784 | 39 | 22.0% |
| Knollwood, IL | 1,684 | 39 | 22.0% |
| City | Population | Air Quality Index | National Avg. |
| Rouse, CA | 1,684 | 49 | 2.0% |
| Princeville, IL | 1,684 | 41 | 18.0% |
| Cassopolis, MI | 1,684 | 39 | 22.0% |
| East Helena, MT | 1,684 | 40 | 20.0% |
| Sturgeon Lake 154, AB | 1,684 | n/a | |
| Knollwood, IL | 1,684 | 39 | 22.0% |
Here are the best places to live in Illinois
Check out the 10 most dangerous cities in Illinois
Most Dangerous States In The US
Check out the 10 safest cities in Illinois