| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 6°F | 24°F | 15°F | 0.5" |
| February | 5°F | 26°F | 15°F | 0.3" |
| March | 19°F | 41°F | 30°F | 1.1" |
| April | 31°F | 55°F | 42°F | 2.3" |
| May | 42°F | 68°F | 54°F | 3.2" |
| June | 51°F | 75°F | 63°F | 4.8" |
| July | 55°F | 80°F | 67°F | 4.9" |
| August | 53°F | 77°F | 65°F | 5.0" |
| September | 45°F | 70°F | 57°F | 3.2" |
| October | 36°F | 57°F | 45°F | 2.6" |
| November | 25°F | 42°F | 33°F | 1.6" |
| December | 12°F | 27°F | 20°F | 1.2" |
| Index | Merrill | Wisconsin | National |
| Air quality index | 34 | 69 | 42 |
| Pollution index | 4,968,600 | 2,842,418 | 2,726,193 |
| Measurement | Total |
| Days measured | 205 |
| Days with good air quality | 196 |
| Days with moderate air quality | 9 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.020% |
| Benzene | 0.060% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.030% |
| Mercury | 0.040% |
| City | Population | Air Quality Index | National Avg. |
| Brokaw, WI | 237 | 34 | 32.0% |
| Maine, WI | 2,577 | 34 | 32.0% |
| Merrill, WI | 9,081 | 34 | 32.0% |
| City | Population | Air Quality Index | National Avg. |
| Boulder Hill, IL | 9,081 | 55 | 10.0% |
| Innsbrook, VA | 9,081 | 44 | 12.0% |
| San Elizario, TX | 9,079 | 53 | 6.0% |
| Saint-Rémi, QC | 9,079 | n/a | |
| Rochelle, IL | 9,083 | 42 | 16.0% |
| Merrill, WI | 9,081 | 34 | 32.0% |
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