Tustin, California has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 12.5 °C (low) to 24.1 °C (high). Annual precipitation averages 327.7 Millimeters. Tustin is located in USDA Plant Hardiness Zone 10b.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 7.9 °C | 19.9 °C | 71.88 mm |
| February | 8.4 °C | 19.8 °C | 84.07 mm |
| March | 9.8 °C | 20.7 °C | 48.01 mm |
| April | 11 °C | 22.9 °C | 18.03 mm |
| May | 13.4 °C | 23.8 °C | 7.62 mm |
| June | 15.4 °C | 25.8 °C | 2.29 mm |
| July | 17.3 °C | 28.4 °C | 1.52 mm |
| August | 17.7 °C | 29.6 °C | 0.25 mm |
| September | 16.7 °C | 29.3 °C | 3.3 mm |
| October | 14 °C | 26.8 °C | 12.19 mm |
| November | 10.2 °C | 22.8 °C | 20.83 mm |
| December | 7.6 °C | 19.7 °C | 57.66 mm |
| Annual | 12.5 °C | 24.1 °C | 327.65 mm |
| Average First Frost Date | No Frost |
| Average Last Frost Date | |
| Average Days With Frost | Frost Free |
| Plant Hardiness Zone | Zone 10b : 1.7°C to 4.4°C |
| Plant Hardiness Zone - 2012 | Zone 10a : -1.1°C to 1.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |