| 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 7b: 5°F to 10°F Zone 7a: 0°F to 5°F |
| 1990 Hardiness Zone: | Zone 7a: 0F to 5F |
| Average First Frost Date: | Oct. 1 - Oct. 10 |
| Average Last Frost Date: | Apr. 21 - Apr. 30 |
| Koppen-Geiger Climate Zone: | BSk - Cold Semi-Arid Climate |
| Ecoregion: | 10e - Pleistocene Lake Basins |
| Heat Zone Days: | 31 - 45 days Over 86°F |
Annual Climate Data for ZIP Code 99350 - Prosser, WA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 25 | 29 | 34 | 38 | 45 | 51 | 55 | 54 | 47 | 38 | 32 | 26 | 39 |
| Avg Max Temp (°F) | 40 | 47 | 57 | 66 | 74 | 81 | 88 | 88 | 79 | 67 | 50 | 40 | 65 |
| Avg Precip (In.) | .95 | .7 | .67 | .64 | .66 | .56 | .24 | .35 | .48 | .65 | 1.02 | 1.17 | 8.08 |