Washington, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.4 °C (low) to 21 °C (high). Annual precipitation averages 1496.6 Millimeters. Washington is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 0.8 °C | 11 °C | 261.87 mm |
| February | 1.3 °C | 12.9 °C | 246.13 mm |
| March | 2.4 °C | 15.4 °C | 227.08 mm |
| April | 4 °C | 17.9 °C | 125.73 mm |
| May | 7.4 °C | 22.8 °C | 77.72 mm |
| June | 10.6 °C | 28.2 °C | 22.35 mm |
| July | 14.2 °C | 32.6 °C | 1.52 mm |
| August | 13.8 °C | 32.4 °C | 3.56 mm |
| September | 11.3 °C | 29.6 °C | 13.46 mm |
| October | 7.1 °C | 23.3 °C | 73.66 mm |
| November | 2.9 °C | 15.3 °C | 154.43 mm |
| December | 0.9 °C | 10.4 °C | 289.05 mm |
| Annual | 6.4 °C | 21 °C | 1496.56 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| 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 | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |