| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 32°F | 48°F | 40°F | 4.7" |
| February | 33°F | 53°F | 42°F | 3.9" |
| March | 40°F | 60°F | 50°F | 5.0" |
| April | 43°F | 62°F | 52°F | 3.7" |
| May | 48°F | 71°F | 59°F | 4.0" |
| June | 52°F | 73°F | 62°F | 2.7" |
| July | 58°F | 83°F | 70°F | 1.3" |
| August | 56°F | 84°F | 68°F | 6.4" |
| September | 49°F | 75°F | 62°F | 0.9" |
| October | 47°F | 64°F | 54°F | 4.5" |
| November | 36°F | 53°F | 44°F | 7.9" |
| December | 35°F | 46°F | 40°F | 10.3" |
| Index | West Haven-Sylvan | Oregon | National |
| Air quality index | 38 | 32 | 42 |
| Pollution index | 3,247,580 | 7,156,356 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 285 |
| Days with moderate air quality | 77 |
| Days w/ poor A.Q. for sensitive groups | 3 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.002% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.500% |
| Lead | 0.040% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Brush Prairie, WA | 2,721 | 38 | 24.0% |
| Bull Mountain, OR | 9,732 | 38 | 24.0% |
| Gladstone, OR | 12,316 | 38 | 24.0% |
| Lake Oswego, OR | 39,476 | 38 | 24.0% |
| Oatfield, OR | 13,588 | 38 | 24.0% |
| West Haven-Sylvan, OR | 8,505 | 38 | 24.0% |
| City | Population | Air Quality Index | National Avg. |
| Reserve, LA | 8,506 | 30 | 40.0% |
| Live Oak city, CA | 8,501 | 35 | 30.0% |
| Alamo Heights, TX | 8,501 | 49 | 2.0% |
| Indian Harbour Beach, FL | 8,509 | 36 | 28.0% |
| Perryville, MO | 8,500 | 54 | 8.0% |
| West Haven-Sylvan, OR | 8,505 | 38 | 24.0% |
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