Ben Lomond, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 45.1 °F (low) to 73.2 °F (high). Annual precipitation averages 48.6 Inches. Ben Lomond is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 38.7 °F | 61.1 °F | 10.49 in. |
| February | 40.0 °F | 62.6 °F | 10.2 in. |
| March | 41.5 °F | 66.0 °F | 6.44 in. |
| April | 43.0 °F | 71.0 °F | 2.99 in. |
| May | 46.5 °F | 75.8 °F | 1.14 in. |
| June | 49.5 °F | 81.7 °F | 0.28 in. |
| July | 52.2 °F | 84.8 °F | 0.02 in. |
| August | 52.0 °F | 85.6 °F | 0.05 in. |
| September | 50.4 °F | 84.4 °F | 0.14 in. |
| October | 46.3 °F | 78.3 °F | 2.2 in. |
| November | 42.0 °F | 67.0 °F | 4.25 in. |
| December | 38.5 °F | 59.8 °F | 10.44 in. |
| Annual | 45.1 °F | 73.2 °F | 48.64 in. |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 30-40 Days |
| Plant Hardiness Zone | Zone 9a : 20°F to 25°F |
| Plant Hardiness Zone - 2012 | Zone 9a : 20°F to 25°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |