| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 33°F | 25°F | 1.1" |
| February | 19°F | 34°F | 26°F | 1.4" |
| March | 30°F | 48°F | 38°F | 1.8" |
| April | 39°F | 60°F | 49°F | 2.7" |
| May | 49°F | 71°F | 60°F | 3.6" |
| June | 60°F | 81°F | 69°F | 4.7" |
| July | 65°F | 85°F | 74°F | 4.0" |
| August | 64°F | 83°F | 73°F | 4.4" |
| September | 56°F | 76°F | 66°F | 2.7" |
| October | 45°F | 64°F | 54°F | 3.2" |
| November | 34°F | 50°F | 42°F | 1.7" |
| December | 23°F | 37°F | 30°F | 2.0" |
| Index | Barrington | Illinois | National |
| Air quality index | 55 | 41 | 42 |
| Pollution index | 543,516 | 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 | 0.000% |
| Benzene | 0.004% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| McHenry, IL | 26,889 | 39 | 22.0% |
| Park City, IL | 7,636 | 39 | 22.0% |
| Island Lake, IL | 8,112 | 39 | 22.0% |
| Waukegan, IL | 87,157 | 39 | 22.0% |
| Hainesville, IL | 3,595 | 39 | 22.0% |
| Barrington, IL | 10,442 | 55 | 10.0% |
| City | Population | Air Quality Index | National Avg. |
| Bellefontaine Neighbors, MO | 10,441 | 54 | 8.0% |
| Budd Lake, NJ | 10,444 | 34 | 32.0% |
| Mount Sinai, NY | 10,446 | 43 | 14.0% |
| Elizabethtown-Kitley, ON | 10,437 | n/a | |
| Ponoka County, AB | 10,437 | n/a | |
| Barrington, IL | 10,442 | 55 | 10.0% |
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