| 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 | 130 | 33 | 34.0% |
| Williams, MN | 253 | 33 | 34.0% |
| City | Population | Air Quality Index | National Avg. |
| Lead Hill, AR | 253 | 36 | 28.0% |
| Lost Bridge Village, AR | 253 | 44 | 12.0% |
| Del Muerto, AZ | 253 | 17 | 66.0% |
| Benton, CA | 253 | 47 | 6.0% |
| Cressey, CA | 253 | 48 | 4.0% |
| Williams, MN | 253 | 33 | 34.0% |