| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 11°F | 27°F | 19°F | 1.8" |
| February | 13°F | 30°F | 21°F | 1.8" |
| March | 25°F | 45°F | 34°F | 4.2" |
| April | 36°F | 58°F | 46°F | 6.0" |
| May | 47°F | 70°F | 58°F | 4.7" |
| June | 57°F | 78°F | 67°F | 9.0" |
| July | 60°F | 83°F | 71°F | 5.9" |
| August | 59°F | 80°F | 69°F | 7.4" |
| September | 51°F | 73°F | 61°F | 5.8" |
| October | 41°F | 60°F | 49°F | 5.8" |
| November | 29°F | 46°F | 37°F | 4.1" |
| December | 17°F | 31°F | 24°F | 2.7" |
| Index | Merrimac | Wisconsin | National |
| Air quality index | 35 | 69 | 42 |
| Pollution index | 350,021 | 2,842,418 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 311 |
| Days with moderate air quality | 53 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.003% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.001% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Lake Wisconsin, WI | 4,573 | 35 | 30.0% |
| Poynette, WI | 2,507 | 35 | 30.0% |
| West Baraboo, WI | 1,519 | 35 | 30.0% |
| Lodi, WI | 3,073 | 35 | 30.0% |
| Prairie du Sac, WI | 4,397 | 35 | 30.0% |
| Merrimac, WI | 672 | 35 | 30.0% |
| City | Population | Air Quality Index | National Avg. |
| Grafton, IL | 672 | 54 | 8.0% |
| Seneca Gardens, KY | 672 | 49 | 2.0% |
| Grand Isle, LA | 672 | 41 | 18.0% |
| Campbell, NY | 672 | 35 | 30.0% |
| Nelsonville, NY | 672 | 36 | 28.0% |
| Merrimac, WI | 672 | 35 | 30.0% |
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