| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 14°F | 30°F | 22°F | 2.3" |
| February | 14°F | 31°F | 23°F | 2.8" |
| March | 26°F | 45°F | 35°F | 3.7" |
| April | 36°F | 58°F | 46°F | 5.9" |
| May | 46°F | 71°F | 58°F | 4.8" |
| June | 56°F | 79°F | 67°F | 7.8" |
| July | 59°F | 82°F | 70°F | 11.4" |
| August | 57°F | 81°F | 68°F | 5.4" |
| September | 50°F | 74°F | 61°F | 7.1" |
| October | 40°F | 61°F | 50°F | 5.8" |
| November | 29°F | 48°F | 38°F | 5.2" |
| December | 19°F | 34°F | 27°F | 3.3" |
| Index | Delavan | Wisconsin | National |
| Air quality index | 37 | 69 | 42 |
| Pollution index | 151,096 | 2,842,418 | 2,726,193 |
| Measurement | Total |
| Days measured | 205 |
| Days with good air quality | 189 |
| Days with moderate air quality | 15 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.002% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.010% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Lake Geneva, WI | 7,872 | 37 | 26.0% |
| Como, WI | 2,064 | 37 | 26.0% |
| Williams Bay, WI | 2,607 | 37 | 26.0% |
| Fontana-on-Geneva Lake, WI | 1,518 | 37 | 26.0% |
| Walworth, WI | 2,835 | 37 | 26.0% |
| Delavan, WI | 8,296 | 37 | 26.0% |
| City | Population | Air Quality Index | National Avg. |
| Mystic Island, NJ | 8,296 | 37 | 26.0% |
| Haledon, NJ | 8,298 | 51 | 2.0% |
| Applewood, CO | 8,300 | 58 | 16.0% |
| Boonville, MO | 8,300 | 38 | 24.0% |
| Charlestown, IN | 8,290 | 49 | 2.0% |
| Delavan, WI | 8,296 | 37 | 26.0% |
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