Mission Viejo, California has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 11.8 °C (low) to 23.8 °C (high). Annual precipitation averages 381.8 Millimeters. Mission Viejo is located in USDA Plant Hardiness Zone 10b.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 8 °C | 19.9 °C | 76.96 mm |
| February | 8.1 °C | 19.8 °C | 94.49 mm |
| March | 8.9 °C | 20.7 °C | 56.13 mm |
| April | 10.1 °C | 22.1 °C | 23.88 mm |
| May | 12.4 °C | 23 °C | 8.13 mm |
| June | 14.4 °C | 25.2 °C | 5.33 mm |
| July | 16.3 °C | 28.3 °C | 2.79 mm |
| August | 16.7 °C | 29.2 °C | 0.76 mm |
| September | 15.8 °C | 28.9 °C | 3.3 mm |
| October | 13.4 °C | 26.3 °C | 17.53 mm |
| November | 10.1 °C | 22.8 °C | 26.92 mm |
| December | 7.7 °C | 19.5 °C | 65.53 mm |
| Annual | 11.8 °C | 23.8 °C | 381.75 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 |