| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 14°F | 37°F | 26°F | 0.6" |
| February | 15°F | 41°F | 27°F | 0.6" |
| March | 23°F | 53°F | 37°F | 1.0" |
| April | 27°F | 60°F | 42°F | 1.6" |
| May | 36°F | 69°F | 51°F | 2.5" |
| June | 44°F | 83°F | 64°F | 1.2" |
| July | 52°F | 92°F | 72°F | 2.3" |
| August | 50°F | 89°F | 69°F | 1.1" |
| September | 42°F | 79°F | 59°F | 0.9" |
| October | 32°F | 64°F | 46°F | 1.3" |
| November | 23°F | 51°F | 36°F | 0.5" |
| December | 12°F | 36°F | 24°F | 0.9" |
| Index | Mills | Wyoming | National |
| Air quality index | 42 | 39 | 42 |
| Pollution index | 873,248 | 1,779,975 | 2,726,193 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 327 |
| Days with moderate air quality | 37 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.050% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.020% |
| Mercury | 0.140% |
| City | Population | Air Quality Index | National Avg. |
| Brookhurst, WY | 114 | 42 | 16.0% |
| Bessemer Bend, WY | 122 | 42 | 16.0% |
| Homa Hills, WY | 196 | 42 | 16.0% |
| Evansville, WY | 2,974 | 42 | 16.0% |
| Casper, WY | 58,287 | 42 | 16.0% |
| Mills, WY | 3,955 | 42 | 16.0% |
| City | Population | Air Quality Index | National Avg. |
| Wonder Lake, IL | 3,955 | 39 | 22.0% |
| Ashland, MO | 3,956 | 38 | 24.0% |
| Weaverville, NC | 3,956 | 44 | 12.0% |
| Lake San Marcos, CA | 3,957 | 64 | 28.0% |
| Southgate, KY | 3,957 | 54 | 8.0% |
| Mills, WY | 3,955 | 42 | 16.0% |
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