| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | -2°F | 18°F | 7°F | 0.5" |
| February | -1°F | 21°F | 9°F | 0.4" |
| March | 15°F | 37°F | 25°F | 1.0" |
| April | 30°F | 53°F | 40°F | 1.1" |
| May | 42°F | 65°F | 53°F | 3.1" |
| June | 52°F | 74°F | 63°F | 4.1" |
| July | 57°F | 80°F | 68°F | 3.6" |
| August | 54°F | 78°F | 65°F | 3.1" |
| September | 47°F | 69°F | 57°F | 2.9" |
| October | 36°F | 54°F | 44°F | 2.6" |
| November | 22°F | 37°F | 29°F | 0.9" |
| December | 4°F | 20°F | 12°F | 0.4" |
| Index | Williams | Minnesota | National |
| Air quality index | 33 | 35 | 42 |
| Pollution index | 1,015,090 | 1,854,519 | 2,726,193 |
| Measurement | Total |
| Days measured | 363 |
| Days with good air quality | 327 |
| Days with moderate air quality | 34 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.010% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Roosevelt, MN | 126 | 33 | 34.0% |
| Williams, MN | 243 | 33 | 34.0% |
| City | Population | Air Quality Index | National Avg. |
| Koyuk, AK | 243 | 38 | 24.0% |
| Malcolm, AL | 243 | 42 | 16.0% |
| East Globe, AZ | 243 | 60 | 20.0% |
| McNeal, AZ | 243 | 45 | 10.0% |
| Bloomfield, CA | 243 | 34 | 32.0% |
| Williams, MN | 243 | 33 | 34.0% |
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