Morton, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 4.3 °C (low) to 15.8 °C (high). Annual precipitation averages 1782.1 Millimeters. Morton is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -0.1 °C | 6.9 °C | 261.11 mm |
| February | 0.1 °C | 8.9 °C | 175.26 mm |
| March | 1.2 °C | 11.3 °C | 193.8 mm |
| April | 2.9 °C | 14.4 °C | 148.84 mm |
| May | 5.9 °C | 18.7 °C | 109.22 mm |
| June | 8.4 °C | 21.7 °C | 78.49 mm |
| July | 10.1 °C | 25.4 °C | 22.86 mm |
| August | 9.9 °C | 26.2 °C | 29.21 mm |
| September | 7.4 °C | 22.9 °C | 70.36 mm |
| October | 4.1 °C | 16.7 °C | 165.86 mm |
| November | 1.5 °C | 10 °C | 267.46 mm |
| December | -0.4 °C | 6.4 °C | 259.59 mm |
| Annual | 4.3 °C | 15.8 °C | 1782.06 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |