Fountain Valley, California has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 12.9 °C (low) to 22.7 °C (high). Annual precipitation averages 305.6 Millimeters. Fountain Valley is located in USDA Plant Hardiness Zone 10b.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 8.3 °C | 19.6 °C | 72.64 mm |
| February | 8.9 °C | 19.4 °C | 79.76 mm |
| March | 10.3 °C | 20.1 °C | 42.93 mm |
| April | 11.5 °C | 21.2 °C | 14.99 mm |
| May | 13.9 °C | 21.9 °C | 6.6 mm |
| June | 15.8 °C | 23.4 °C | 2.03 mm |
| July | 17.7 °C | 25.8 °C | 1.52 mm |
| August | 18 °C | 27.1 °C | 0 mm |
| September | 17.2 °C | 26.9 °C | 2.54 mm |
| October | 14.6 °C | 24.9 °C | 11.43 mm |
| November | 10.7 °C | 22.3 °C | 18.29 mm |
| December | 8 °C | 19.4 °C | 52.83 mm |
| Annual | 12.9 °C | 22.7 °C | 305.56 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 |