| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 32°F | 47°F | 39°F | 5.6" |
| February | 34°F | 50°F | 42°F | 5.2" |
| March | 37°F | 55°F | 45°F | 6.7" |
| April | 39°F | 61°F | 49°F | 4.5" |
| May | 45°F | 68°F | 56°F | 4.4" |
| June | 49°F | 73°F | 61°F | 2.4" |
| July | 52°F | 80°F | 65°F | 1.6" |
| August | 53°F | 81°F | 67°F | 2.6" |
| September | 48°F | 74°F | 60°F | 4.9" |
| October | 43°F | 62°F | 52°F | 6.9" |
| November | 36°F | 53°F | 44°F | 7.3" |
| December | 32°F | 46°F | 38°F | 6.4" |
| Index | La Grande | Washington | National |
| Air quality index | 30 | 36 | 42 |
| Pollution index | 6,915,950 | 4,541,850 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 323 |
| Days with moderate air quality | 42 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.110% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.000% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Alder, WA | 134 | 20 | 60.0% |
| Elbe, WA | 46 | 20 | 60.0% |
| Mineral, WA | 135 | 20 | 60.0% |
| Ashford, WA | 489 | 20 | 60.0% |
| McKenna, WA | 623 | 30 | 40.0% |
| La Grande, WA | 88 | 30 | 40.0% |
| City | Population | Air Quality Index | National Avg. |
| Beaver, AK | 88 | 38 | 24.0% |
| Nondalton, AK | 88 | 31 | 38.0% |
| Casmalia, CA | 88 | 46 | 8.0% |
| Furnace Creek, CA | 88 | 15 | 70.0% |
| Long Barn, CA | 88 | 39 | 22.0% |
| La Grande, WA | 88 | 30 | 40.0% |
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