| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 23°F | 36°F | 29°F | 1.8" |
| February | 27°F | 45°F | 35°F | 2.1" |
| March | 33°F | 55°F | 43°F | 2.4" |
| April | 36°F | 61°F | 48°F | 1.5" |
| May | 44°F | 72°F | 57°F | 3.7" |
| June | 50°F | 77°F | 62°F | 2.0" |
| July | 57°F | 91°F | 74°F | 3.7" |
| August | 53°F | 87°F | 69°F | 2.6" |
| September | 45°F | 75°F | 59°F | 2.5" |
| October | 39°F | 60°F | 48°F | 1.6" |
| November | 30°F | 44°F | 37°F | 2.4" |
| December | 23°F | 35°F | 29°F | 3.9" |
| Index | Millwood | 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. |
| State Line, ID | 14 | 43 | 14.0% |
| Country Homes, WA | 5,877 | 43 | 14.0% |
| Otis Orchards-East Farms, WA | 5,968 | 43 | 14.0% |
| Airway Heights, WA | 8,885 | 43 | 14.0% |
| Green Bluff, WA | 366 | 43 | 14.0% |
| Millwood, WA | 1,742 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Lost Hills, CA | 1,742 | 67 | 34.0% |
| Port Barrington, IL | 1,742 | 55 | 10.0% |
| Pittsville, MD | 1,742 | 36 | 28.0% |
| Nisswa, MN | 1,742 | 29 | 42.0% |
| South Browning, MT | 1,742 | 37 | 26.0% |
| Millwood, WA | 1,742 | 43 | 14.0% |
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