| 2023 Hardiness Zone: | Zone 10b: 35°F to 40°F Zone 10a: 30°F to 35°F | |
| 2012 Hardiness Zone: | Zone 10a: 30°F to 35°F | |
| 1990 Hardiness Zone: | Zone 10a: 30F to 35F | |
| Average First Frost Date: | Frost Rare | |
| Average Last Frost Date: | Jan. 21 - Jan. 31 | |
| Koppen-Geiger Climate Zone: | Csa - Hot-Summer Mediterranean Climate | |
| Ecoregion: | ||
| Current Drought Status: | Exceptional Drought | |
| Heat Zone Days: | 61 - 90 days Over 86°F |
Annual Climate Data for ZIP Code 91765 - Diamond Bar, CA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 42 | 44 | 45 | 47 | 52 | 55 | 59 | 59 | 58 | 53 | 45 | 41 | 50 |
| Avg Max Temp (°F) | 68 | 69 | 69 | 74 | 77 | 83 | 89 | 90 | 87 | 81 | 73 | 69 | 77 |
| Avg Precip (In.) | 4.16 | 4.33 | 3.69 | .96 | .37 | .08 | .03 | .15 | .38 | .65 | 1.42 | 2.24 | 18.47 |