| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 31°F | 47°F | 38°F | 5.1" |
| February | 32°F | 53°F | 41°F | 5.3" |
| March | 38°F | 60°F | 48°F | 5.2" |
| April | 40°F | 62°F | 50°F | 3.9" |
| May | 46°F | 71°F | 57°F | 5.5" |
| June | 49°F | 73°F | 60°F | 2.7" |
| July | 55°F | 83°F | 68°F | 2.0" |
| August | 53°F | 83°F | 67°F | 4.3" |
| September | 46°F | 75°F | 60°F | 1.1" |
| October | 44°F | 63°F | 52°F | 4.1" |
| November | 34°F | 52°F | 42°F | 8.4" |
| December | 33°F | 46°F | 39°F | 13.3" |
| Index | Scappoose | 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. |
| St. Helens, OR | 13,779 | 18 | 64.0% |
| Vernonia, OR | 2,158 | 18 | 64.0% |
| Woodland, WA | 6,223 | 18 | 64.0% |
| Columbia City, OR | 1,770 | 18 | 64.0% |
| Deer Island, OR | 105 | 18 | 64.0% |
| Scappoose, OR | 7,436 | 38 | 24.0% |
| City | Population | Air Quality Index | National Avg. |
| Georgetown, DE | 7,436 | 36 | 28.0% |
| Ellwood City, PA | 7,436 | 31 | 38.0% |
| Whitinsville, MA | 7,435 | 40 | 20.0% |
| Clarkston, WA | 7,435 | 29 | 42.0% |
| Montpelier, VT | 7,434 | 37 | 26.0% |
| Scappoose, OR | 7,436 | 38 | 24.0% |
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