| 2023 Hardiness Zone: | Zone 9a: 20°F to 25°F Zone 9b: 25°F to 30°F Zone 10a: 30°F to 35°F |
| 2012 Hardiness Zone: | Zone 9a: 20°F to 25°F Zone 9b: 25°F to 30°F Zone 10a: 30°F to 35°F |
| 1990 Hardiness Zone: | Zone 9b: 25F to 30F |
| Average First Frost Date: | Dec. 1 - Dec. 10 |
| Average Last Frost Date: | Mar. 1 - Mar. 10 |
| Koppen-Geiger Climate Zone: | Csb - Warm-Summer Mediterranean Climate |
| Ecoregion: | |
| Heat Zone Days: | 15 - 30 days Over 86°F |
Annual Climate Data for ZIP Code 94558 - Napa, CA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 38 | 41 | 43 | 44 | 49 | 52 | 55 | 55 | 53 | 49 | 42 | 38 | 46 |
| Avg Max Temp (°F) | 57 | 62 | 65 | 70 | 76 | 82 | 85 | 84 | 83 | 77 | 64 | 57 | 72 |
| Avg Precip (In.) | 5.17 | 5.12 | 4.04 | 1.38 | .75 | .17 | .05 | .1 | .36 | 1.39 | 3.61 | 3.9 | 26.03 |