| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 29°F | 43°F | 35°F | 1.8" |
| February | 33°F | 49°F | 39°F | 1.4" |
| March | 38°F | 58°F | 47°F | 2.6" |
| April | 42°F | 64°F | 52°F | 2.0" |
| May | 49°F | 74°F | 60°F | 1.8" |
| June | 55°F | 82°F | 67°F | 1.5" |
| July | 63°F | 93°F | 77°F | 0.3" |
| August | 62°F | 91°F | 76°F | 0.2" |
| September | 54°F | 81°F | 66°F | 0.6" |
| October | 44°F | 66°F | 54°F | 1.7" |
| November | 36°F | 51°F | 43°F | 2.3" |
| December | 28°F | 41°F | 34°F | 2.5" |
| Index | College Place | Washington | National |
| Air quality index | 23 | 36 | 42 |
| Pollution index | 697,942 | 4,541,850 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 318 |
| Days with moderate air quality | 47 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.020% |
| Benzene | 0.004% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.010% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Walla Walla East, WA | 2,459 | 23 | 54.0% |
| Milton-Freewater, OR | 7,044 | 23 | 54.0% |
| Garrett, WA | 1,815 | 23 | 54.0% |
| Umapine, OR | 537 | 23 | 54.0% |
| Touchet, WA | 357 | 23 | 54.0% |
| College Place, WA | 9,311 | 23 | 54.0% |
| City | Population | Air Quality Index | National Avg. |
| North College Hill, OH | 9,310 | 54 | 8.0% |
| Leisure World, MD | 9,314 | 47 | 6.0% |
| Eagle Point, OR | 9,316 | 36 | 28.0% |
| Hartland, WI | 9,317 | 44 | 12.0% |
| Flossmoor, IL | 9,318 | 55 | 10.0% |
| College Place, WA | 9,311 | 23 | 54.0% |
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