| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 36°F | 49°F | 42°F | 5.1" |
| February | 37°F | 52°F | 44°F | 3.8" |
| March | 40°F | 55°F | 47°F | 4.9" |
| April | 43°F | 61°F | 51°F | 3.1" |
| May | 49°F | 68°F | 57°F | 2.2" |
| June | 54°F | 72°F | 62°F | 1.5" |
| July | 58°F | 79°F | 67°F | 0.4" |
| August | 58°F | 79°F | 68°F | 0.6" |
| September | 54°F | 73°F | 62°F | 1.6" |
| October | 47°F | 62°F | 54°F | 3.9" |
| November | 40°F | 53°F | 47°F | 6.6" |
| December | 36°F | 48°F | 41°F | 6.1" |
| Index | Seattle | Washington | National |
| Air quality index | 45 | 36 | 42 |
| Pollution index | 1,081,430 | 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 | 0.000% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Manchester, WA | 6,050 | 18 | 64.0% |
| Rocky Point, WA | 1,418 | 18 | 64.0% |
| Burley, WA | 2,515 | 18 | 64.0% |
| Poulsbo, WA | 10,869 | 18 | 64.0% |
| East Port Orchard, WA | 5,069 | 18 | 64.0% |
| Seattle, WA | 741,251 | 45 | 10.0% |
| City | Population | Air Quality Index | National Avg. |
| Brampton, ON | 735,754 | n/a | |
| Mississauga, ON | 764,342 | n/a | |
| Denver, CO | 715,878 | 58 | 16.0% |
| Winnipeg, MB | 775,440 | n/a | |
| Washington, DC | 701,974 | 47 | 6.0% |
| Seattle, WA | 741,251 | 45 | 10.0% |
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