| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 24°F | 37°F | 30°F | 2.8" |
| February | 28°F | 46°F | 35°F | 2.1" |
| March | 34°F | 54°F | 43°F | 2.0" |
| April | 36°F | 59°F | 47°F | 1.8" |
| May | 43°F | 69°F | 55°F | 2.0" |
| June | 46°F | 73°F | 59°F | 2.0" |
| July | 51°F | 88°F | 70°F | 0.9" |
| August | 48°F | 86°F | 67°F | 1.2" |
| September | 41°F | 73°F | 56°F | 1.4" |
| October | 39°F | 61°F | 49°F | 2.4" |
| November | 31°F | 45°F | 37°F | 2.7" |
| December | 24°F | 35°F | 30°F | 2.9" |
| Index | Steptoe | Washington | National |
| Air quality index | 18 | 36 | 42 |
| Pollution index | 1,232,200 | 4,541,850 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 354 |
| Days with moderate air quality | 11 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.020% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Palouse, WA | 969 | 10 | 80.0% |
| Farmington, WA | 142 | 10 | 80.0% |
| Garfield, WA | 586 | 18 | 64.0% |
| Albion, WA | 677 | 18 | 64.0% |
| Oakesdale, WA | 412 | 18 | 64.0% |
| Steptoe, WA | 135 | 18 | 64.0% |
| City | Population | Air Quality Index | National Avg. |
| Atqasuk, AK | 135 | 38 | 24.0% |
| Fort Greely, AK | 135 | 38 | 24.0% |
| Mono City, CA | 135 | 47 | 6.0% |
| San Acacio, CO | 135 | 15 | 70.0% |
| Mount Union, IA | 135 | 32 | 36.0% |
| Steptoe, WA | 135 | 18 | 64.0% |
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