Twain, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 2.9 °C (low) to 21 °C (high). Annual precipitation averages 1005.8 Millimeters. Twain is located in USDA Plant Hardiness Zone 8a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -1.9 °C | 9.7 °C | 177.29 mm |
| February | -1.6 °C | 12.1 °C | 164.08 mm |
| March | 0.2 °C | 14.9 °C | 153.16 mm |
| April | 1.4 °C | 19.1 °C | 81.03 mm |
| May | 4.8 °C | 23.8 °C | 51.82 mm |
| June | 7.9 °C | 29.3 °C | 20.07 mm |
| July | 10.3 °C | 33.9 °C | 2.54 mm |
| August | 8.7 °C | 33.6 °C | 3.05 mm |
| September | 5.4 °C | 30.2 °C | 9.14 mm |
| October | 1.7 °C | 22.9 °C | 50.29 mm |
| November | -0.2 °C | 13.9 °C | 97.54 mm |
| December | -2.3 °C | 8.6 °C | 195.83 mm |
| Annual | 2.9 °C | 21 °C | 1005.84 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 8a : -12.2°C to -9.4°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |