Boulder Creek, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 44.5 °F (low) to 71.7 °F (high). Annual precipitation averages 49.9 Inches. Boulder Creek is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Mar. 11 - Mar. 20 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 38.1 °F | 60.6 °F | 9.98 in. |
| February | 39.5 °F | 62.4 °F | 10.59 in. |
| March | 40.9 °F | 65.5 °F | 7.23 in. |
| April | 42.4 °F | 67.7 °F | 3.31 in. |
| May | 45.9 °F | 73.1 °F | 1.25 in. |
| June | 48.8 °F | 79.7 °F | 0.37 in. |
| July | 51.7 °F | 83.4 °F | 0.02 in. |
| August | 51.5 °F | 83.8 °F | 0.05 in. |
| September | 49.6 °F | 82.3 °F | 0.15 in. |
| October | 45.7 °F | 75.7 °F | 2.24 in. |
| November | 41.4 °F | 66.9 °F | 4.53 in. |
| December | 38.1 °F | 59.5 °F | 10.14 in. |
| Annual | 44.5 °F | 71.7 °F | 49.86 in. |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 11 - Mar. 20 |
| Average Days With Frost | 30-40 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 | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |