| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 32°F | 47°F | 39°F | 6.9" |
| February | 32°F | 52°F | 41°F | 3.7" |
| March | 39°F | 58°F | 47°F | 6.2" |
| April | 41°F | 60°F | 49°F | 4.1" |
| May | 46°F | 68°F | 56°F | 2.9" |
| June | 50°F | 69°F | 59°F | 2.5" |
| July | 54°F | 78°F | 66°F | 2.9" |
| August | 53°F | 78°F | 64°F | 4.9" |
| September | 47°F | 70°F | 58°F | 4.4" |
| October | 44°F | 61°F | 51°F | 4.5" |
| November | 36°F | 50°F | 42°F | 6.6" |
| December | 34°F | 45°F | 39°F | 9.5" |
| Index | McMillin | Washington | National |
| Air quality index | 30 | 36 | 42 |
| Pollution index | 17,693,800 | 4,541,850 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 323 |
| Days with moderate air quality | 42 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.300% |
| Carbon Tetrachloride | 0.050% |
| Lead | 0.110% |
| Mercury | 0.020% |
| City | Population | Air Quality Index | National Avg. |
| Dash Point, WA | 1,008 | 18 | 64.0% |
| Tacoma, WA | 215,766 | 18 | 64.0% |
| Ruston, WA | 1,329 | 18 | 64.0% |
| Browns Point, WA | 961 | 18 | 64.0% |
| McChord AFB, WA | 3,268 | 30 | 40.0% |
| McMillin, WA | 1,236 | 30 | 40.0% |
| City | Population | Air Quality Index | National Avg. |
| March ARB, CA | 1,236 | 89 | 78.0% |
| Boyce, LA | 1,236 | 30 | 40.0% |
| Frazeysburg, OH | 1,236 | 41 | 18.0% |
| New Hope, OR | 1,236 | 26 | 48.0% |
| Fivepointville, PA | 1,236 | 42 | 16.0% |
| McMillin, WA | 1,236 | 30 | 40.0% |
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