| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 33°F | 47°F | 39°F | 7.4" |
| February | 33°F | 51°F | 41°F | 4.9" |
| March | 36°F | 55°F | 44°F | 6.1" |
| April | 38°F | 60°F | 48°F | 4.0" |
| May | 44°F | 67°F | 55°F | 4.5" |
| June | 49°F | 72°F | 60°F | 3.0" |
| July | 52°F | 80°F | 65°F | 1.5" |
| August | 52°F | 80°F | 65°F | 3.4" |
| September | 48°F | 73°F | 60°F | 4.4" |
| October | 42°F | 62°F | 51°F | 6.3" |
| November | 36°F | 52°F | 44°F | 8.2" |
| December | 32°F | 46°F | 38°F | 6.9" |
| Index | Steilacoom | Washington | National |
| Air quality index | 30 | 36 | 42 |
| Pollution index | 6,704,330 | 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 | 0.003% |
| Benzene | 0.100% |
| Carbon Tetrachloride | 0.004% |
| Lead | 0.030% |
| Mercury | 0.003% |
| City | Population | Air Quality Index | National Avg. |
| Browns Point, WA | 961 | 18 | 64.0% |
| Allyn, WA | 2,504 | 18 | 64.0% |
| Key Center, WA | 3,631 | 18 | 64.0% |
| Ruston, WA | 1,329 | 18 | 64.0% |
| Canterwood, WA | 3,070 | 18 | 64.0% |
| Steilacoom, WA | 6,366 | 30 | 40.0% |
| City | Population | Air Quality Index | National Avg. |
| Fowler, CA | 6,366 | 60 | 20.0% |
| Gray, LA | 6,366 | 41 | 18.0% |
| Hamlet, NC | 6,366 | 30 | 40.0% |
| Brunswick, MD | 6,364 | 40 | 20.0% |
| Air Force Academy, CO | 6,368 | 45 | 10.0% |
| Steilacoom, WA | 6,366 | 30 | 40.0% |
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