Willow Creek, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 44.2 °F (low) to 72.7 °F (high). Annual precipitation averages 50.6 Inches. Willow Creek is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 36.8 °F | 51.8 °F | 9.12 in. |
| February | 37.8 °F | 56.8 °F | 6.85 in. |
| March | 39.3 °F | 62.3 °F | 6.91 in. |
| April | 41.5 °F | 69.5 °F | 4.02 in. |
| May | 45.8 °F | 78.7 °F | 1.9 in. |
| June | 50.0 °F | 87.0 °F | 0.7 in. |
| July | 54.5 °F | 95.4 °F | 0.11 in. |
| August | 53.5 °F | 95.9 °F | 0.11 in. |
| September | 49.5 °F | 90.5 °F | 0.63 in. |
| October | 44.3 °F | 75.5 °F | 3.22 in. |
| November | 40.6 °F | 58.7 °F | 6.38 in. |
| December | 36.8 °F | 50.4 °F | 10.64 in. |
| Annual | 44.2 °F | 72.7 °F | 50.59 in. |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 20-30 Days |
| Plant Hardiness Zone | Zone 9a : 20°F to 25°F |
| Plant Hardiness Zone - 2012 | Zone 9a : 20°F to 25°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |