| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 21°F | 35°F | 28°F | 3.5" |
| February | 24°F | 40°F | 31°F | 1.7" |
| March | 27°F | 48°F | 36°F | 2.0" |
| April | 32°F | 58°F | 44°F | 1.8" |
| May | 38°F | 69°F | 53°F | 1.6" |
| June | 45°F | 75°F | 59°F | 2.6" |
| July | 49°F | 87°F | 69°F | 0.6" |
| August | 47°F | 86°F | 66°F | 0.8" |
| September | 39°F | 77°F | 57°F | 0.7" |
| October | 31°F | 57°F | 43°F | 2.3" |
| November | 28°F | 43°F | 35°F | 3.0" |
| December | 18°F | 32°F | 25°F | 4.1" |
| Index | Clayton | Washington | National |
| Air quality index | 43 | 36 | 42 |
| Pollution index | 408,717 | 4,541,850 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 252 |
| Days with moderate air quality | 111 |
| Days w/ poor A.Q. for sensitive groups | 2 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.001% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Deer Park, WA | 4,209 | 43 | 14.0% |
| Loon Lake, WA | 689 | 43 | 14.0% |
| Green Bluff, WA | 366 | 43 | 14.0% |
| Springdale, WA | 477 | 43 | 14.0% |
| Valley, WA | 122 | 43 | 14.0% |
| Clayton, WA | 361 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Poyen, AR | 361 | 38 | 24.0% |
| Sadieville, KY | 361 | 42 | 16.0% |
| Hopkins, MO | 361 | 43 | 14.0% |
| Casar, NC | 361 | 36 | 28.0% |
| Weston, NE | 361 | 31 | 38.0% |
| Clayton, WA | 361 | 43 | 14.0% |
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