| 2023 Hardiness Zone: | Zone 7b: 5°F to 10°F Zone 7a: 0°F to 5°F |
| 2012 Hardiness Zone: | Zone 6b: -5°F to 0°F Zone 7a: 0°F to 5°F |
| 1990 Hardiness Zone: | Zone 6b: -5F to 0F |
| Average First Frost Date: | Oct. 21 - Oct. 31 |
| Average Last Frost Date: | Apr. 11 - Apr. 20 |
| Koppen-Geiger Climate Zone: | Csa - Hot-Summer Mediterranean Climate |
| Ecoregion: | 10e - Pleistocene Lake Basins |
| Heat Zone Days: | 31 - 45 days Over 86°F |
Annual Climate Data for ZIP Code 99362 - Walla Walla, WA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 28 | 32 | 36 | 41 | 47 | 54 | 60 | 60 | 51 | 42 | 35 | 29 | 43 |
| Avg Max Temp (°F) | 41 | 47 | 56 | 64 | 72 | 80 | 89 | 88 | 79 | 65 | 50 | 41 | 64 |
| Avg Precip (In.) | 1.98 | 1.72 | 1.92 | 1.58 | 1.74 | 1.14 | .56 | .72 | .79 | 1.55 | 2.44 | 2.13 | 18.28 |