Jamestown, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 8.5 °C (low) to 23.4 °C (high). Annual precipitation averages 756.9 Millimeters. Jamestown is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 2.7 °C | 13.5 °C | 151.38 mm |
| February | 3.4 °C | 15.2 °C | 130.05 mm |
| March | 4.9 °C | 17.8 °C | 115.57 mm |
| April | 6.4 °C | 20.2 °C | 64.77 mm |
| May | 9.4 °C | 25.5 °C | 36.58 mm |
| June | 12.9 °C | 30.8 °C | 8.64 mm |
| July | 16.3 °C | 34.8 °C | 0.76 mm |
| August | 15.8 °C | 34.3 °C | 1.78 mm |
| September | 13.6 °C | 31.6 °C | 4.57 mm |
| October | 9.3 °C | 25.6 °C | 37.08 mm |
| November | 5.1 °C | 18.3 °C | 72.9 mm |
| December | 2.4 °C | 13.4 °C | 132.84 mm |
| Annual | 8.5 °C | 23.4 °C | 756.92 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 40-50 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 | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |