| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 33°F | 46°F | 39°F | 10.0" |
| February | 33°F | 50°F | 41°F | 6.7" |
| March | 36°F | 54°F | 44°F | 9.7" |
| April | 37°F | 60°F | 47°F | 4.7" |
| May | 43°F | 67°F | 54°F | 3.1" |
| June | 48°F | 72°F | 58°F | 1.6" |
| July | 51°F | 79°F | 63°F | 0.8" |
| August | 51°F | 80°F | 64°F | 1.1" |
| September | 47°F | 74°F | 59°F | 3.0" |
| October | 42°F | 61°F | 50°F | 7.4" |
| November | 36°F | 51°F | 43°F | 13.6" |
| December | 32°F | 45°F | 38°F | 11.5" |
| Index | Shelton | Washington | National |
| Air quality index | 21 | 36 | 42 |
| Pollution index | 2,873,390 | 4,541,850 | 2,726,193 |
| Measurement | Total |
| Days measured | 361 |
| Days with good air quality | 339 |
| Days with moderate air quality | 22 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.050% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.010% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Allyn, WA | 2,504 | 18 | 64.0% |
| Grapeview, WA | 703 | 18 | 64.0% |
| Elma, WA | 3,299 | 20 | 60.0% |
| Herron Island, WA | 50 | 21 | 58.0% |
| Skokomish, WA | 635 | 21 | 58.0% |
| Shelton, WA | 10,467 | 21 | 58.0% |
| City | Population | Air Quality Index | National Avg. |
| Bromont, QC | 10,466 | n/a | |
| North Bellport, NY | 10,468 | 43 | 14.0% |
| Wasilla, AK | 10,469 | 31 | 38.0% |
| Cusseta-Chattahoochee County, GA | 10,470 | 42 | 16.0% |
| Covington, LA | 10,471 | 30 | 40.0% |
| Shelton, WA | 10,467 | 21 | 58.0% |
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