| 2023 Hardiness Zone: | Zone 9b: 25°F to 30°F Zone 10a: 30°F to 35°F |
| 2012 Hardiness Zone: | 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: | Jan. 11 - Jan. 20 |
| Average Last Frost Date: | Jan. 21 - Jan. 31 |
| Koppen-Geiger Climate Zone: | Csb - Warm-Summer Mediterranean Climate |
| Ecoregion: | |
| Heat Zone Days: | 46 - 60 days Over 86°F |
Annual Climate Data for ZIP Code 94028 - Portola Valley, CA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 37 | 39 | 40 | 42 | 45 | 48 | 51 | 51 | 49 | 45 | 40 | 36 | 43 |
| Avg Max Temp (°F) | 58 | 61 | 64 | 69 | 74 | 79 | 83 | 83 | 81 | 75 | 64 | 58 | 71 |
| Avg Precip (In.) | 7.39 | 7.16 | 5.61 | 2.41 | .82 | .25 | .07 | .17 | .4 | 1.96 | 4.65 | 5.41 | 36.3 |