Thermalito, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 9.7 °C (low) to 23.8 °C (high). Annual precipitation averages 731.8 Millimeters. Thermalito is located in USDA Plant Hardiness Zone 9b. The growing season typically runs from the last frost around Feb. 11 - Feb. 20 through the first frost around Dec. 11 - Dec. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 3.8 °C | 13.2 °C | 148.34 mm |
| February | 5.1 °C | 16 °C | 127 mm |
| March | 6.4 °C | 18.7 °C | 109.98 mm |
| April | 8.2 °C | 22 °C | 53.85 mm |
| May | 11.5 °C | 26.9 °C | 34.54 mm |
| June | 14.7 °C | 31.6 °C | 9.65 mm |
| July | 17.1 °C | 34.8 °C | 0.51 mm |
| August | 15.9 °C | 34.1 °C | 1.78 mm |
| September | 14.2 °C | 31.6 °C | 5.33 mm |
| October | 10.3 °C | 25.9 °C | 35.05 mm |
| November | 6 °C | 18.1 °C | 71.12 mm |
| December | 3.6 °C | 13.1 °C | 134.62 mm |
| Annual | 9.7 °C | 23.8 °C | 731.77 mm |
| Average First Frost Date | Dec. 11 - Dec. 20 |
| Average Last Frost Date | Feb. 11 - Feb. 20 |
| Average Days With Frost | 10-20 Days |
| Plant Hardiness Zone | Zone 9b : -3.9°C to -1.1°C |
| Plant Hardiness Zone - 2012 | Zone 9b : -3.9°C to -1.1°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |