Twain Harte, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 42.6 °F (low) to 68.3 °F (high). Annual precipitation averages 41.2 Inches. 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 | 31.9 °F | 52.5 °F | 7.39 in. |
| February | 32.1 °F | 53.7 °F | 6.42 in. |
| March | 34.7 °F | 57.5 °F | 5.86 in. |
| April | 37.3 °F | 61.8 °F | 3.72 in. |
| May | 43.8 °F | 70.7 °F | 2.36 in. |
| June | 50.6 °F | 80.9 °F | 0.78 in. |
| July | 57.8 °F | 89.0 °F | 0.08 in. |
| August | 58.0 °F | 88.6 °F | 0.09 in. |
| September | 53.3 °F | 82.9 °F | 0.42 in. |
| October | 43.8 °F | 71.7 °F | 2.48 in. |
| November | 36.4 °F | 59.1 °F | 4.38 in. |
| December | 31.7 °F | 51.4 °F | 7.26 in. |
| Annual | 42.6 °F | 68.3 °F | 41.24 in. |
| 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 : 15°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 8b : 15°F to 20°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |