Twain Harte, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 5.9 °C (low) to 20.2 °C (high). Annual precipitation averages 1047.5 Millimeters. Twain Harte is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -0.1 °C | 11.4 °C | 187.71 mm |
| February | 0.1 °C | 12.1 °C | 163.07 mm |
| March | 1.5 °C | 14.2 °C | 148.84 mm |
| April | 2.9 °C | 16.6 °C | 94.49 mm |
| May | 6.6 °C | 21.5 °C | 59.94 mm |
| June | 10.3 °C | 27.2 °C | 19.81 mm |
| July | 14.3 °C | 31.7 °C | 2.03 mm |
| August | 14.4 °C | 31.4 °C | 2.29 mm |
| September | 11.8 °C | 28.3 °C | 10.67 mm |
| October | 6.6 °C | 22.1 °C | 62.99 mm |
| November | 2.4 °C | 15.1 °C | 111.25 mm |
| December | -0.2 °C | 10.8 °C | 184.4 mm |
| Annual | 5.9 °C | 20.2 °C | 1047.49 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |