| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 20°F | 34°F | 26°F | 1.9" |
| February | 21°F | 36°F | 28°F | 1.6" |
| March | 33°F | 49°F | 40°F | 2.4" |
| April | 42°F | 62°F | 51°F | 3.6" |
| May | 52°F | 73°F | 61°F | 4.3" |
| June | 63°F | 82°F | 72°F | 4.6" |
| July | 68°F | 86°F | 76°F | 3.5" |
| August | 67°F | 83°F | 75°F | 5.1" |
| September | 60°F | 77°F | 68°F | 2.8" |
| October | 48°F | 65°F | 55°F | 3.9" |
| November | 36°F | 51°F | 43°F | 2.2" |
| December | 25°F | 37°F | 31°F | 2.2" |
| Index | Ashburn | Chicago | Illinois |
| Air quality index | 55 | 55 | 41 |
| Pollution index | 80,238,704 | 80,238,704 | 3,148,694 |
| 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 | 0.760% |
| Benzene | 0.560% |
| Carbon Tetrachloride | 0.280% |
| Lead | 0.480% |
| Mercury | 0.480% |
| City | Population | Air Quality Index | National Avg. |
| Hillside, IL | 7,937 | 55 | 10.0% |
| Westchester, IL | 16,255 | 55 | 10.0% |
| Darien, IL | 21,843 | 55 | 10.0% |
| Oak Brook, IL | 8,085 | 55 | 10.0% |
| Willowbrook, IL | 8,610 | 55 | 10.0% |
| Chicago, IL | 2,699,347 | 55 | 10.0% |
| City | Population | Air Quality Index | National Avg. |
| Toronto, ON | 3,013,752 | n/a | |
| Houston, TX | 2,313,238 | 52 | 4.0% |
| Montréal, QC | 1,811,008 | n/a | |
| Phoenix, AZ | 1,658,422 | 74 | 48.0% |
| Philadelphia, PA | 1,581,531 | 51 | 2.0% |
| Chicago, IL | 2,699,347 | 55 | 10.0% |
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