| 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 7a: 0F to 5F | |
| Average First Frost Date: | Oct. 21 - Oct. 31 | |
| Average Last Frost Date: | Apr. 21 - Apr. 30 | |
| Koppen-Geiger Climate Zone: | BWk - Cold Desert Climate | |
| Ecoregion: | 10e - Pleistocene Lake Basins | |
| Current Drought Status: | Exceptional Drought | |
| Heat Zone Days: | 46 - 60 days Over 86°F |
Annual Climate Data for ZIP Code 99349 - Mattawa, WA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 25 | 29 | 35 | 41 | 49 | 56 | 61 | 61 | 52 | 41 | 33 | 26 | 42 |
| Avg Max Temp (°F) | 39 | 47 | 57 | 66 | 74 | 82 | 90 | 89 | 80 | 66 | 49 | 39 | 65 |
| Avg Precip (In.) | .78 | .63 | .61 | .43 | .48 | .35 | .15 | .26 | .32 | .46 | .91 | 1.07 | 6.46 |