| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 16°F | 32°F | 24°F | 1.4" |
| February | 17°F | 33°F | 25°F | 1.5" |
| March | 28°F | 45°F | 36°F | 2.6" |
| April | 37°F | 57°F | 46°F | 4.1" |
| May | 47°F | 68°F | 57°F | 3.7" |
| June | 57°F | 77°F | 67°F | 4.5" |
| July | 63°F | 82°F | 72°F | 4.4" |
| August | 62°F | 80°F | 71°F | 3.7" |
| September | 55°F | 73°F | 64°F | 3.3" |
| October | 44°F | 62°F | 52°F | 3.4" |
| November | 33°F | 49°F | 40°F | 2.0" |
| December | 22°F | 36°F | 29°F | 2.5" |
| Index | Winthrop Harbor | Illinois | National |
| Air quality index | 39 | 41 | 50 |
| Pollution index | 3,131,700 | 3,347,295 | 5,066,862 |
| Measurement | Total |
| Days measured | 203 |
| Days with good air quality | 174 |
| Days with moderate air quality | 28 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.004% |
| Mercury | 0.360% |
| City, State | Population | Air Quality Index | National Avg. |
| Antioch, IL | 14,342 | 39 | 22% |
| Libertyville, IL | 20,435 | 39 | 22% |
| Venetian Village, IL | 2,623 | 39 | 22% |
| Round Lake Heights, IL | 3,110 | 39 | 22% |
| Wadsworth, IL | 3,646 | 39 | 22% |
| Winthrop Harbor, IL | 6,832 | 39 | 22% |
| City, State | Population | Air Quality Index | National Avg. |
| Greenville, IL | 6,833 | 43 | 14% |
| Milford, OH | 6,833 | 54 | 8% |
| Whitinsville, MA | 6,831 | 40 | 20% |
| Barrington, NJ | 6,831 | 51 | 2% |
| Mountainside, NJ | 6,835 | 51 | 2% |
| Winthrop Harbor, IL | 6,832 | 39 | 22% |
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