Boulder Creek, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.9 °C (low) to 22.1 °C (high). Annual precipitation averages 1266.5 Millimeters. 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 | 3.4 °C | 15.9 °C | 253.49 mm |
| February | 4.2 °C | 16.9 °C | 268.99 mm |
| March | 4.9 °C | 18.6 °C | 183.64 mm |
| April | 5.8 °C | 19.8 °C | 84.07 mm |
| May | 7.7 °C | 22.8 °C | 31.75 mm |
| June | 9.3 °C | 26.5 °C | 9.4 mm |
| July | 10.9 °C | 28.6 °C | 0.51 mm |
| August | 10.8 °C | 28.8 °C | 1.27 mm |
| September | 9.8 °C | 27.9 °C | 3.81 mm |
| October | 7.6 °C | 24.3 °C | 56.9 mm |
| November | 5.2 °C | 19.4 °C | 115.06 mm |
| December | 3.4 °C | 15.3 °C | 257.56 mm |
| Annual | 6.9 °C | 22.1 °C | 1266.45 mm |
| 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 : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 9a : -6.7°C to -3.9°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |