| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 16°F | 34°F | 25°F | 2.3" |
| February | 18°F | 36°F | 27°F | 2.3" |
| March | 29°F | 49°F | 39°F | 2.8" |
| April | 38°F | 63°F | 50°F | 3.9" |
| May | 48°F | 73°F | 60°F | 5.4" |
| June | 59°F | 83°F | 71°F | 4.5" |
| July | 64°F | 86°F | 75°F | 5.2" |
| August | 63°F | 84°F | 74°F | 4.4" |
| September | 56°F | 78°F | 66°F | 3.6" |
| October | 44°F | 65°F | 54°F | 3.4" |
| November | 32°F | 52°F | 42°F | 2.3" |
| December | 21°F | 38°F | 29°F | 2.9" |
| Index | Rosemont | 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. |
| Kildeer, IL | 4,007 | 55 | 10.0% |
| Arlington Heights, IL | 75,071 | 55 | 10.0% |
| Chicago, IL | 2,699,347 | 55 | 10.0% |
| Forest View, IL | 1,312 | 55 | 10.0% |
| Evanston, IL | 73,979 | 55 | 10.0% |
| Rosemont, IL | 4,173 | 55 | 10.0% |
| City | Population | Air Quality Index | National Avg. |
| Magee, MS | 4,174 | 44 | 12.0% |
| Minersville, PA | 4,174 | 42 | 16.0% |
| Chelan, WA | 4,174 | 24 | 52.0% |
| West Laurel, MD | 4,171 | 47 | 6.0% |
| Westville, NJ | 4,171 | 51 | 2.0% |
| Rosemont, IL | 4,173 | 55 | 10.0% |
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