| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 13°F | 28°F | 21°F | 1.1" |
| February | 13°F | 29°F | 21°F | 1.3" |
| March | 25°F | 42°F | 33°F | 2.0" |
| April | 35°F | 54°F | 44°F | 3.9" |
| May | 45°F | 67°F | 55°F | 3.6" |
| June | 55°F | 76°F | 65°F | 4.2" |
| July | 60°F | 82°F | 70°F | 3.4" |
| August | 59°F | 79°F | 68°F | 3.0" |
| September | 51°F | 72°F | 61°F | 2.5" |
| October | 41°F | 59°F | 50°F | 3.1" |
| November | 30°F | 47°F | 38°F | 1.7" |
| December | 19°F | 33°F | 26°F | 1.9" |
| Index | Plymouth | Wisconsin | National |
| Air quality index | 38 | 69 | 42 |
| Pollution index | 3,923,560 | 2,842,418 | 2,726,193 |
| Measurement | Total |
| Days measured | 206 |
| Days with good air quality | 180 |
| Days with moderate air quality | 24 |
| Days w/ poor A.Q. for sensitive groups | 2 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.040% |
| Benzene | 0.050% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.070% |
| Mercury | 0.100% |
| City | Population | Air Quality Index | National Avg. |
| Mount Calvary, WI | 602 | 36 | 28.0% |
| Greenbush, WI | 194 | 36 | 28.0% |
| St. Cloud, WI | 504 | 36 | 28.0% |
| New Holstein, WI | 3,116 | 36 | 28.0% |
| Oostburg, WI | 3,017 | 38 | 24.0% |
| Plymouth, WI | 8,654 | 38 | 24.0% |
| City | Population | Air Quality Index | National Avg. |
| Des Peres, MO | 8,654 | 54 | 8.0% |
| Wharton, TX | 8,654 | 52 | 4.0% |
| Edgemere, MD | 8,652 | 46 | 8.0% |
| South Bruce Peninsula, ON | 8,652 | n/a | |
| Audubon, NJ | 8,656 | 51 | 2.0% |
| Plymouth, WI | 8,654 | 38 | 24.0% |
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