| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 20°F | 37°F | 28°F | 3.9" |
| February | 18°F | 39°F | 28°F | 2.3" |
| March | 28°F | 48°F | 37°F | 4.1" |
| April | 36°F | 61°F | 48°F | 3.2" |
| May | 47°F | 70°F | 58°F | 4.6" |
| June | 56°F | 78°F | 66°F | 5.8" |
| July | 60°F | 80°F | 71°F | 2.9" |
| August | 61°F | 81°F | 71°F | 4.8" |
| September | 56°F | 77°F | 66°F | 10.0" |
| October | 46°F | 67°F | 56°F | 4.7" |
| November | 36°F | 55°F | 45°F | 4.0" |
| December | 27°F | 42°F | 34°F | 2.8" |
| Index | Willoughby | Ohio | National |
| Air quality index | 50 | 40 | 42 |
| Pollution index | 28,421,300 | 4,472,386 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 185 |
| Days with moderate air quality | 173 |
| Days w/ poor A.Q. for sensitive groups | 7 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.220% |
| Benzene | 0.280% |
| Carbon Tetrachloride | 0.170% |
| Lead | 0.250% |
| Mercury | 0.090% |
| City | Population | Air Quality Index | National Avg. |
| Painesville, OH | 19,817 | 34 | 32.0% |
| Perry, OH | 1,662 | 34 | 32.0% |
| Fairport Harbor, OH | 3,067 | 34 | 32.0% |
| Grand River, OH | 604 | 34 | 32.0% |
| Beachwood, OH | 11,627 | 50 | = 100 |
| Willoughby, OH | 22,904 | 50 | = 100 |
| City | Population | Air Quality Index | National Avg. |
| Webster Groves, MO | 22,906 | 54 | 8.0% |
| Uxbridge, ON | 22,892 | n/a | |
| Derry, NH | 22,891 | 37 | 26.0% |
| Marshall, TX | 22,881 | 38 | 24.0% |
| Dickinson, ND | 22,880 | 33 | 34.0% |
| Willoughby, OH | 22,904 | 50 | = 100 |
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