| 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 | Algonquin | Illinois | National |
| Air quality index | 42 | 41 | 42 |
| Pollution index | 543,516 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 341 |
| Days with good air quality | 240 |
| Days with moderate air quality | 100 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| 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. |
| Prairie Grove, IL | 2,023 | 39 | 22.0% |
| Long Lake, IL | 3,065 | 39 | 22.0% |
| McCullom Lake, IL | 1,193 | 39 | 22.0% |
| Lakemoor, IL | 5,820 | 39 | 22.0% |
| Hainesville, IL | 3,595 | 39 | 22.0% |
| Algonquin, IL | 30,848 | 42 | 16.0% |
| City | Population | Air Quality Index | National Avg. |
| Sterling, VA | 30,872 | 47 | 6.0% |
| Los Altos, CA | 30,878 | 43 | 14.0% |
| Fair Oaks, CA | 30,882 | 52 | 4.0% |
| Cleburne, TX | 30,812 | 33 | 34.0% |
| Centre Wellington, ON | 30,896 | n/a | |
| Algonquin, IL | 30,848 | 42 | 16.0% |
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