| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 36°F | 48°F | 41°F | 4.7" |
| February | 37°F | 51°F | 44°F | 3.2" |
| March | 40°F | 55°F | 46°F | 4.5" |
| April | 43°F | 61°F | 50°F | 2.9" |
| May | 48°F | 68°F | 57°F | 2.1" |
| June | 53°F | 73°F | 62°F | 1.6" |
| July | 58°F | 80°F | 67°F | 0.5" |
| August | 58°F | 80°F | 67°F | 0.9" |
| September | 53°F | 73°F | 62°F | 1.8" |
| October | 47°F | 62°F | 53°F | 3.9" |
| November | 40°F | 53°F | 46°F | 5.7" |
| December | 36°F | 47°F | 41°F | 4.5" |
| Index | Covington | Washington | National |
| Air quality index | 45 | 36 | 42 |
| Pollution index | 17,693,800 | 4,541,850 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 236 |
| Days with moderate air quality | 127 |
| Days w/ poor A.Q. for sensitive groups | 2 |
| 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% |
| Midland, WA | 9,518 | 30 | 40.0% |
| Summit, WA | 8,993 | 30 | 40.0% |
| Puyallup, WA | 41,666 | 30 | 40.0% |
| Waller, WA | 7,672 | 30 | 40.0% |
| Covington, WA | 21,131 | 45 | 10.0% |
| City | Population | Air Quality Index | National Avg. |
| Ashland, OR | 21,138 | 36 | 28.0% |
| Saint-Augustin-de-Desmaures, QC | 21,143 | n/a | |
| Arnold, MO | 21,144 | 54 | 8.0% |
| Easley, SC | 21,149 | 46 | 8.0% |
| Piqua, OH | 21,159 | 47 | 6.0% |
| Covington, WA | 21,131 | 45 | 10.0% |
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