Julian, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 8.1 °C (low) to 20.6 °C (high). Annual precipitation averages 671.6 Millimeters. Julian is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 3.2 °C | 12.9 °C | 131.57 mm |
| February | 2.9 °C | 12.7 °C | 147.32 mm |
| March | 4 °C | 15.2 °C | 106.93 mm |
| April | 4.8 °C | 17.3 °C | 48.77 mm |
| May | 7.6 °C | 21.1 °C | 21.59 mm |
| June | 11.9 °C | 26.7 °C | 3.3 mm |
| July | 16 °C | 30.3 °C | 7.62 mm |
| August | 16.1 °C | 30.9 °C | 11.94 mm |
| September | 13.3 °C | 28.2 °C | 12.19 mm |
| October | 8.9 °C | 22.4 °C | 27.69 mm |
| November | 5.6 °C | 16.9 °C | 54.86 mm |
| December | 2.7 °C | 12.4 °C | 97.79 mm |
| Annual | 8.1 °C | 20.6 °C | 671.57 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 9a : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |