| 2023 Hardiness Zone: | Zone 6b: -5°F to 0°F Zone 7b: 5°F to 10°F Zone 7a: 0°F to 5°F |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 6b: -5°F to 0°F Zone 7b: 5°F to 10°F Zone 7a: 0°F to 5°F |
| 1990 Hardiness Zone: | Zone 6a: -10F to -5F |
| Average First Frost Date: | Sep. 21 - Sep. 30 |
| Average Last Frost Date: | May 11 - May 20 |
| Koppen-Geiger Climate Zone: | Dsb - Humid Continental Climate - Dry Cool Summer |
| Ecoregion: | 10h - Palouse Hills |
| Heat Zone Days: | 1 - 7 days Over 86°F |
Annual Climate Data for ZIP Code 99163 - Pullman, WA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 24 | 27 | 31 | 36 | 41 | 46 | 50 | 50 | 43 | 36 | 30 | 24 | 36 |
| Avg Max Temp (°F) | 35 | 42 | 49 | 57 | 65 | 72 | 82 | 83 | 74 | 60 | 43 | 36 | 58 |
| Avg Precip (In.) | 2.64 | 2.21 | 2.14 | 1.8 | 1.88 | 1.41 | .88 | .92 | .94 | 1.56 | 3.07 | 2.92 | 22.38 |