| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 41°F | 31°F | 1.1" |
| February | 25°F | 50°F | 37°F | 0.8" |
| March | 30°F | 59°F | 44°F | 0.8" |
| April | 34°F | 67°F | 51°F | 0.5" |
| May | 42°F | 77°F | 60°F | 1.0" |
| June | 48°F | 83°F | 67°F | 0.4" |
| July | 55°F | 93°F | 76°F | 0.1" |
| August | 53°F | 92°F | 73°F | 0.2" |
| September | 44°F | 82°F | 63°F | 0.4" |
| October | 36°F | 67°F | 50°F | 0.8" |
| November | 27°F | 52°F | 39°F | 0.9" |
| December | 20°F | 40°F | 29°F | 1.5" |
| Index | Ahtanum | Washington | National |
| Air quality index | 38 | 36 | 42 |
| Pollution index | 1,140,980 | 4,541,850 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 227 |
| Days with moderate air quality | 128 |
| Days w/ poor A.Q. for sensitive groups | 10 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Donald, WA | 0 | 38 | 24.0% |
| Harrah, WA | 626 | 38 | 24.0% |
| Selah, WA | 7,957 | 38 | 24.0% |
| Tieton, WA | 2,053 | 38 | 24.0% |
| White Swan, WA | 793 | 38 | 24.0% |
| Ahtanum, WA | 3,701 | 38 | 24.0% |
| City | Population | Air Quality Index | National Avg. |
| Upland, IN | 3,701 | 35 | 30.0% |
| Village Green, NY | 3,701 | 37 | 26.0% |
| Rockfish, NC | 3,700 | 41 | 18.0% |
| Midland, NC | 3,702 | 49 | 2.0% |
| Merchantville, NJ | 3,702 | 51 | 2.0% |
| Ahtanum, WA | 3,701 | 38 | 24.0% |
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