| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 15°F | 28°F | 21°F | 1.8" |
| February | 15°F | 30°F | 22°F | 1.1" |
| March | 26°F | 43°F | 34°F | 3.6" |
| April | 36°F | 56°F | 45°F | 7.5" |
| May | 47°F | 68°F | 56°F | 4.1" |
| June | 56°F | 77°F | 66°F | 4.1" |
| July | 60°F | 81°F | 70°F | 1.5" |
| August | 59°F | 78°F | 68°F | 4.1" |
| September | 51°F | 72°F | 61°F | 5.1" |
| October | 42°F | 59°F | 50°F | 5.8" |
| November | 31°F | 46°F | 38°F | 2.1" |
| December | 20°F | 32°F | 26°F | 4.5" |
| Index | Grafton | Wisconsin | National |
| Air quality index | 44 | 69 | 42 |
| Pollution index | 3,171,080 | 2,842,418 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 254 |
| Days with moderate air quality | 108 |
| Days w/ poor A.Q. for sensitive groups | 3 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.003% |
| Lead | 0.010% |
| Mercury | 0.100% |
| City | Population | Air Quality Index | National Avg. |
| Kewaskum, WI | 4,224 | 36 | 28.0% |
| Belgium, WI | 2,201 | 38 | 24.0% |
| Fredonia, WI | 2,466 | 38 | 24.0% |
| Waubeka, WI | 624 | 38 | 24.0% |
| Port Washington, WI | 11,881 | 44 | 12.0% |
| Grafton, WI | 11,718 | 44 | 12.0% |
| City | Population | Air Quality Index | National Avg. |
| Webster, MA | 11,719 | 40 | 20.0% |
| Florham Park, NJ | 11,719 | 51 | 2.0% |
| Wanaque, NJ | 11,719 | 51 | 2.0% |
| Stratford, PE | 11,716 | n/a | |
| Arlington, TN | 11,715 | 45 | 10.0% |
| Grafton, WI | 11,718 | 44 | 12.0% |
Here are the best places to live in Wisconsin
Check out the 10 safest cities in Wisconsin
Check out the 10 most dangerous cities in Wisconsin
Most Dangerous States In The US