| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 34°F | 47°F | 39°F | 8.0" |
| February | 33°F | 51°F | 40°F | 3.6" |
| March | 36°F | 54°F | 44°F | 4.7" |
| April | 38°F | 58°F | 47°F | 3.1" |
| May | 44°F | 66°F | 54°F | 3.9" |
| June | 49°F | 70°F | 58°F | 3.1" |
| July | 53°F | 79°F | 65°F | 2.0" |
| August | 53°F | 78°F | 64°F | 2.9" |
| September | 48°F | 72°F | 59°F | 3.9" |
| October | 43°F | 61°F | 50°F | 4.5" |
| November | 38°F | 51°F | 44°F | 8.3" |
| December | 32°F | 45°F | 38°F | 6.6" |
| Index | Morton | Washington | National |
| Air quality index | 20 | 36 | 42 |
| Pollution index | 4,215,410 | 4,541,850 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 343 |
| Days with moderate air quality | 22 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.005% |
| Benzene | 0.050% |
| Carbon Tetrachloride | 0.004% |
| Lead | 0.030% |
| Mercury | 0.250% |
| City | Population | Air Quality Index | National Avg. |
| Mineral, WA | 135 | 20 | 60.0% |
| Mossyrock, WA | 666 | 20 | 60.0% |
| Elbe, WA | 46 | 20 | 60.0% |
| Ashford, WA | 489 | 20 | 60.0% |
| Morton, WA | 1,111 | 20 | 60.0% |
| City | Population | Air Quality Index | National Avg. |
| Parker City, IN | 1,111 | 35 | 30.0% |
| Raleigh, MS | 1,111 | 44 | 12.0% |
| Haskins, OH | 1,111 | 40 | 20.0% |
| Souris, PE | 1,111 | n/a | |
| Berens River 13, MB | 1,111 | n/a | |
| Morton, WA | 1,111 | 20 | 60.0% |
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