| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 21°F | 33°F | 26°F | 1.3" |
| February | 24°F | 41°F | 32°F | 1.0" |
| March | 30°F | 54°F | 41°F | 1.4" |
| April | 35°F | 64°F | 49°F | 0.8" |
| May | 43°F | 74°F | 59°F | 1.3" |
| June | 50°F | 81°F | 66°F | 1.3" |
| July | 57°F | 92°F | 75°F | 0.5" |
| August | 56°F | 91°F | 73°F | 0.3" |
| September | 47°F | 80°F | 63°F | 0.4" |
| October | 37°F | 62°F | 49°F | 1.2" |
| November | 28°F | 45°F | 36°F | 1.4" |
| December | 20°F | 33°F | 26°F | 1.8" |
| Index | Tonasket | Washington | National |
| Air quality index | 24 | 36 | 42 |
| Pollution index | 422,626 | 4,541,850 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 298 |
| Days with moderate air quality | 66 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Riverside, WA | 396 | 24 | 52.0% |
| Conconully, WA | 225 | 24 | 52.0% |
| Loomis, WA | 101 | 24 | 52.0% |
| Tonasket, WA | 1,131 | 24 | 52.0% |
| City | Population | Air Quality Index | National Avg. |
| Riverside, ID | 1,131 | 27 | 46.0% |
| White Plains, NC | 1,131 | 45 | 10.0% |
| Omaha, TX | 1,131 | 39 | 22.0% |
| Mossey River, MB | 1,131 | n/a | |
| Clay, CA | 1,130 | 52 | 4.0% |
| Tonasket, WA | 1,131 | 24 | 52.0% |
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