Lake Forest, California has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 11.7 °C (low) to 23.9 °C (high). Annual precipitation averages 368.8 Millimeters. Lake Forest is located in USDA Plant Hardiness Zone 10b.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 7.9 °C | 19.9 °C | 73.66 mm |
| February | 7.9 °C | 19.9 °C | 95 mm |
| March | 8.8 °C | 20.9 °C | 55.12 mm |
| April | 9.9 °C | 22.2 °C | 22.86 mm |
| May | 12.3 °C | 23.2 °C | 8.13 mm |
| June | 14.3 °C | 25.4 °C | 3.81 mm |
| July | 16.3 °C | 28.4 °C | 2.54 mm |
| August | 16.6 °C | 29.5 °C | 0.51 mm |
| September | 15.7 °C | 29.1 °C | 3.05 mm |
| October | 13.3 °C | 26.3 °C | 16 mm |
| November | 9.9 °C | 22.9 °C | 26.42 mm |
| December | 7.5 °C | 19.6 °C | 61.72 mm |
| Annual | 11.7 °C | 23.9 °C | 368.82 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 |