| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 24°F | 35°F | 29°F | 0.8" |
| February | 28°F | 44°F | 35°F | 0.7" |
| March | 34°F | 55°F | 43°F | 0.9" |
| April | 40°F | 63°F | 51°F | 0.6" |
| May | 48°F | 74°F | 60°F | 1.0" |
| June | 55°F | 81°F | 67°F | 0.4" |
| July | 63°F | 91°F | 76°F | 0.2" |
| August | 62°F | 89°F | 75°F | 0.3" |
| September | 53°F | 79°F | 65°F | 0.3" |
| October | 42°F | 63°F | 52°F | 0.7" |
| November | 32°F | 47°F | 38°F | 0.9" |
| December | 23°F | 34°F | 28°F | 1.1" |
| Index | Rock Island | Washington | National |
| Air quality index | 24 | 36 | 42 |
| Pollution index | 422,626 | 4,541,850 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 298 |
| Days with moderate air quality | 66 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| South Wenatchee, WA | 1,351 | 24 | 52.0% |
| Sunnyslope, WA | 3,761 | 24 | 52.0% |
| Wenatchee, WA | 34,249 | 24 | 52.0% |
| East Wenatchee, WA | 14,012 | 24 | 52.0% |
| Quincy, WA | 7,815 | 24 | 52.0% |
| Rock Island, WA | 1,240 | 24 | 52.0% |
| City | Population | Air Quality Index | National Avg. |
| Wallace, LA | 1,240 | 41 | 18.0% |
| Columbus, NC | 1,240 | 44 | 12.0% |
| Lamèque, NB | 1,240 | n/a | |
| St-Pierre-Jolys, MB | 1,240 | n/a | |
| Manning, AB | 1,240 | n/a | |
| Rock Island, WA | 1,240 | 24 | 52.0% |
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