Walnut Creek, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 9.1 °C (low) to 22.1 °C (high). Annual precipitation averages 612.4 Millimeters. Walnut Creek is located in USDA Plant Hardiness Zone 9b. The growing season typically runs from the last frost around Jan. 21 - Jan. 31 through the first frost around Jan. 1 - Jan. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 4.6 °C | 13.8 °C | 127 mm |
| February | 5.4 °C | 16.1 °C | 121.16 mm |
| March | 6.7 °C | 18.6 °C | 85.85 mm |
| April | 8.1 °C | 20.8 °C | 41.66 mm |
| May | 10.3 °C | 23.7 °C | 20.32 mm |
| June | 12.3 °C | 27.3 °C | 3.05 mm |
| July | 13.6 °C | 29.7 °C | 0.25 mm |
| August | 13.6 °C | 29.7 °C | 1.02 mm |
| September | 12.8 °C | 28.8 °C | 1.78 mm |
| October | 10.3 °C | 24.7 °C | 27.94 mm |
| November | 6.6 °C | 18.3 °C | 59.94 mm |
| December | 4.3 °C | 13.9 °C | 122.43 mm |
| Annual | 9.1 °C | 22.1 °C | 612.4 mm |
| Average First Frost Date | Jan. 1 - Jan. 10 |
| Average Last Frost Date | Jan. 21 - Jan. 31 |
| Average Days With Frost | Frost Rare |
| Plant Hardiness Zone | Zone 9b : -3.9°C to -1.1°C |
| Plant Hardiness Zone - 2012 | Zone 9b : -3.9°C to -1.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |