Walla Walla, Washington has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 5.6 °C (low) to 17.9 °C (high). Annual precipitation averages 431.3 Millimeters. Walla Walla is located in USDA Plant Hardiness Zone 7b. 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 | -1.6 °C | 5.4 °C | 49.02 mm |
| February | -0.6 °C | 8.3 °C | 38.61 mm |
| March | 1.9 °C | 13.3 °C | 44.7 mm |
| April | 4.5 °C | 17.3 °C | 44.45 mm |
| May | 8.2 °C | 22.1 °C | 46.99 mm |
| June | 11.4 °C | 26.1 °C | 31.24 mm |
| July | 14.6 °C | 31.9 °C | 9.14 mm |
| August | 14.2 °C | 31.6 °C | 11.18 mm |
| September | 9.9 °C | 26.2 °C | 16.51 mm |
| October | 5 °C | 18 °C | 36.58 mm |
| November | 0.9 °C | 9.8 °C | 49.78 mm |
| December | -1.7 °C | 5 °C | 53.09 mm |
| Annual | 5.6 °C | 17.9 °C | 431.29 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7b : -15°C to -12.2°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |