Fullerton, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 54.8 °F (low) to 75.9 °F (high). Annual precipitation averages 13.1 Inches. Fullerton is located in USDA Plant Hardiness Zone 10b.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 46.5 °F | 68.5 °F | 3.12 in. |
| February | 47.5 °F | 68.5 °F | 3.36 in. |
| March | 50.0 °F | 70.0 °F | 1.94 in. |
| April | 52.2 °F | 73.2 °F | 0.64 in. |
| May | 56.6 °F | 75.2 °F | 0.27 in. |
| June | 60.2 °F | 78.8 °F | 0.08 in. |
| July | 63.6 °F | 84.0 °F | 0.04 in. |
| August | 64.2 °F | 85.9 °F | 0.0 in. |
| September | 62.5 °F | 85.1 °F | 0.12 in. |
| October | 57.7 °F | 80.4 °F | 0.49 in. |
| November | 50.8 °F | 73.7 °F | 0.77 in. |
| December | 45.6 °F | 68.0 °F | 2.22 in. |
| Annual | 54.8 °F | 75.9 °F | 13.05 in. |
| Average First Frost Date | No Frost |
| Average Last Frost Date | |
| Average Days With Frost | Frost Free |
| Plant Hardiness Zone | Zone 10b : 35°F to 30°F |
| Plant Hardiness Zone - 2012 | Zone 10b : 35°F to 30°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |