| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 16°F | 32°F | 24°F | 1.4" |
| February | 17°F | 34°F | 25°F | 1.2" |
| March | 30°F | 49°F | 38°F | 2.2" |
| April | 39°F | 62°F | 50°F | 3.8" |
| May | 49°F | 73°F | 60°F | 4.5" |
| June | 59°F | 82°F | 70°F | 4.4" |
| July | 63°F | 85°F | 74°F | 4.1" |
| August | 62°F | 83°F | 72°F | 3.8" |
| September | 54°F | 77°F | 65°F | 3.4" |
| October | 43°F | 64°F | 53°F | 3.1" |
| November | 32°F | 50°F | 40°F | 1.9" |
| December | 21°F | 36°F | 29°F | 2.1" |
| Index | Bartlett | Illinois | National |
| Air quality index | 55 | 41 | 42 |
| Pollution index | 14,981,300 | 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 | 0.010% |
| Benzene | 0.140% |
| Carbon Tetrachloride | 0.030% |
| Lead | 0.020% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Prestbury, IL | 1,978 | 0 | 100.0% |
| Lake in the Hills, IL | 28,617 | 42 | 16.0% |
| Huntley, IL | 27,413 | 42 | 16.0% |
| Pingree Grove, IL | 8,768 | 42 | 16.0% |
| Algonquin, IL | 30,848 | 42 | 16.0% |
| Bartlett, IL | 40,894 | 55 | 10.0% |
| City | Population | Air Quality Index | National Avg. |
| Bullhead City, AZ | 40,808 | 13 | 74.0% |
| Wilkes-Barre, PA | 40,805 | 38 | 24.0% |
| Buffalo Grove, IL | 40,804 | 55 | 10.0% |
| Cedar Falls, IA | 40,750 | 39 | 22.0% |
| Manassas, VA | 41,038 | 47 | 6.0% |
| Bartlett, IL | 40,894 | 55 | 10.0% |
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