Fallbrook, California has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 53.3 °F (low) to 75 °F (high). Annual precipitation averages 16.2 Inches. Fallbrook is located in USDA Plant Hardiness Zone 10b. The growing season typically runs from the last frost around Jan. 21 - Jan. 31 through the first frost around Jan. 1 - Jan. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 46.6 °F | 67.4 °F | 3.68 in. |
| February | 46.8 °F | 66.9 °F | 4.02 in. |
| March | 47.8 °F | 67.7 °F | 2.25 in. |
| April | 49.6 °F | 70.9 °F | 1.11 in. |
| May | 53.5 °F | 73.3 °F | 0.33 in. |
| June | 56.8 °F | 78.5 °F | 0.09 in. |
| July | 60.8 °F | 83.6 °F | 0.09 in. |
| August | 62.0 °F | 86.5 °F | 0.03 in. |
| September | 60.9 °F | 85.6 °F | 0.14 in. |
| October | 56.9 °F | 80.0 °F | 0.62 in. |
| November | 51.1 °F | 73.0 °F | 1.13 in. |
| December | 46.4 °F | 66.9 °F | 2.66 in. |
| Annual | 53.3 °F | 75 °F | 16.15 in. |
| Average First Frost Date | Jan. 1 - Jan. 10 |
| Average Last Frost Date | Jan. 21 - Jan. 31 |
| Average Days With Frost | Frost Rare |
| Plant Hardiness Zone | Zone 10b : 35°F to 30°F |
| Plant Hardiness Zone - 2012 | Zone 10b : 35°F to 30°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |