| 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 | Winnetka | Illinois | National |
| Air quality index | 55 | 41 | 42 |
| Pollution index | 3,795,410 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 121 |
| Days with moderate air quality | 227 |
| Days w/ poor A.Q. for sensitive groups | 16 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 0.030% |
| Benzene | 0.050% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.003% |
| Mercury | 0.310% |
| City | Population | Air Quality Index | National Avg. |
| Lake Bluff, IL | 5,540 | 39 | 22.0% |
| Mundelein, IL | 31,574 | 39 | 22.0% |
| Green Oaks, IL | 3,882 | 39 | 22.0% |
| North Chicago, IL | 29,967 | 39 | 22.0% |
| Knollwood, IL | 1,684 | 39 | 22.0% |
| Winnetka, IL | 12,361 | 55 | 10.0% |
| City | Population | Air Quality Index | National Avg. |
| Lakeland Village, CA | 12,362 | 89 | 78.0% |
| Urbana, MD | 12,362 | 40 | 20.0% |
| Larkspur, CA | 12,363 | 40 | 20.0% |
| Wellesley, ON | 12,358 | n/a | |
| Fairfax Station, VA | 12,364 | 47 | 6.0% |
| Winnetka, IL | 12,361 | 55 | 10.0% |
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