Penngrove, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 44.7 °F (low) to 69.4 °F (high). Annual precipitation averages 30.1 Inches. Penngrove is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Feb. 11 - Feb. 20 through the first frost around Dec. 1 - Dec. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 38.1 °F | 57.0 °F | 5.9 in. |
| February | 39.6 °F | 60.6 °F | 5.97 in. |
| March | 41.3 °F | 63.9 °F | 4.1 in. |
| April | 42.8 °F | 66.1 °F | 1.93 in. |
| May | 46.2 °F | 70.7 °F | 1.19 in. |
| June | 49.6 °F | 76.7 °F | 0.28 in. |
| July | 51.6 °F | 79.9 °F | 0.02 in. |
| August | 52.0 °F | 80.4 °F | 0.08 in. |
| September | 49.9 °F | 80.5 °F | 0.13 in. |
| October | 46.3 °F | 75.3 °F | 1.41 in. |
| November | 41.0 °F | 65.0 °F | 3.19 in. |
| December | 37.6 °F | 57.2 °F | 5.94 in. |
| Annual | 44.7 °F | 69.4 °F | 30.14 in. |
| Average First Frost Date | Dec. 1 - Dec. 10 |
| Average Last Frost Date | Feb. 11 - Feb. 20 |
| Average Days With Frost | 10-20 Days |
| Plant Hardiness Zone | Zone 9a : 20°F to 25°F |
| Plant Hardiness Zone - 2012 | Zone 9b : 25°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |