Costa Mesa, California has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 12.8 °C (low) to 22.1 °C (high). Annual precipitation averages 293.4 Millimeters. Costa Mesa is located in USDA Plant Hardiness Zone 10b.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 8.3 °C | 19.5 °C | 66.04 mm |
| February | 8.8 °C | 19.4 °C | 75.69 mm |
| March | 10.2 °C | 20.1 °C | 41.91 mm |
| April | 11.3 °C | 20.3 °C | 16.51 mm |
| May | 13.7 °C | 21.2 °C | 6.35 mm |
| June | 15.6 °C | 22.6 °C | 2.29 mm |
| July | 17.4 °C | 24.8 °C | 1.78 mm |
| August | 17.8 °C | 26 °C | 0.25 mm |
| September | 17 °C | 25.9 °C | 2.79 mm |
| October | 14.4 °C | 24.1 °C | 11.18 mm |
| November | 10.8 °C | 22.3 °C | 18.8 mm |
| December | 8.2 °C | 19.4 °C | 49.78 mm |
| Annual | 12.8 °C | 22.1 °C | 293.37 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 10b : 1.7°C to 4.4°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |