Duvall, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.6 °C (low) to 16 °C (high). Annual precipitation averages 1217.4 Millimeters. Duvall is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.9 °C | 8.2 °C | 157.99 mm |
| February | 1.9 °C | 9.8 °C | 112.78 mm |
| March | 3.3 °C | 12.1 °C | 126.24 mm |
| April | 5.2 °C | 15.1 °C | 105.16 mm |
| May | 8.2 °C | 18.8 °C | 74.42 mm |
| June | 10.6 °C | 21.1 °C | 65.79 mm |
| July | 12.5 °C | 24.8 °C | 26.42 mm |
| August | 12.6 °C | 25.3 °C | 28.19 mm |
| September | 10.3 °C | 22.1 °C | 59.69 mm |
| October | 6.9 °C | 16.1 °C | 120.65 mm |
| November | 3.9 °C | 10.7 °C | 177.04 mm |
| December | 1.7 °C | 7.7 °C | 163.07 mm |
| Annual | 6.6 °C | 16 °C | 1217.44 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |