| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 30°F | 24°F | 1.2" |
| February | 25°F | 44°F | 33°F | 2.4" |
| March | 31°F | 57°F | 43°F | 1.8" |
| April | 35°F | 65°F | 50°F | 1.5" |
| May | 42°F | 75°F | 59°F | 2.6" |
| June | 49°F | 80°F | 64°F | 4.2" |
| July | 58°F | 92°F | 75°F | 1.6" |
| August | 54°F | 91°F | 73°F | 0.8" |
| September | 45°F | 78°F | 61°F | 2.2" |
| October | 37°F | 61°F | 48°F | 2.3" |
| November | 27°F | 41°F | 34°F | 3.6" |
| December | 18°F | 30°F | 25°F | 4.0" |
| Index | Keller | Washington | National |
| Air quality index | 43 | 36 | 42 |
| Pollution index | 2,683,410 | 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 | 0.040% |
| Carbon Tetrachloride | 0.004% |
| Lead | 0.030% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Nespelem, WA | 215 | 18 | 64.0% |
| Coulee Dam, WA | 1,355 | 18 | 64.0% |
| Elmer City, WA | 301 | 18 | 64.0% |
| Grand Coulee, WA | 1,257 | 18 | 64.0% |
| Keller, WA | 204 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Perla, AR | 204 | 38 | 24.0% |
| Bear Valley, CA | 204 | 48 | 4.0% |
| Bloomington, ID | 204 | 44 | 12.0% |
| Eldred, IL | 204 | 54 | 8.0% |
| Indianola, IL | 204 | 42 | 16.0% |
| Keller, WA | 204 | 43 | 14.0% |
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