Hayfork, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 2.4 °C (low) to 21 °C (high). Annual precipitation averages 923.8 Millimeters. Hayfork is located in USDA Plant Hardiness Zone 8a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -1.8 °C | 10 °C | 173.74 mm |
| February | -1.7 °C | 12.6 °C | 138.43 mm |
| March | -0.6 °C | 15.1 °C | 133.1 mm |
| April | 0.8 °C | 18.2 °C | 59.18 mm |
| May | 3.8 °C | 23.3 °C | 40.64 mm |
| June | 6.2 °C | 28.3 °C | 16.76 mm |
| July | 9.3 °C | 33.9 °C | 6.1 mm |
| August | 8.5 °C | 33.6 °C | 4.06 mm |
| September | 5.4 °C | 30.4 °C | 8.64 mm |
| October | 1.6 °C | 22.9 °C | 48.51 mm |
| November | -0.2 °C | 14.3 °C | 103.38 mm |
| December | -2 °C | 9.3 °C | 191.26 mm |
| Annual | 2.4 °C | 21 °C | 923.8 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 40-50 Days |
| Plant Hardiness Zone | Zone 8a : -12.2°C to -9.4°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |