Penngrove, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 7 °C (low) to 20.8 °C (high). Annual precipitation averages 765.6 Millimeters. 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 | 3.4 °C | 13.9 °C | 149.86 mm |
| February | 4.2 °C | 15.9 °C | 151.64 mm |
| March | 5.2 °C | 17.7 °C | 104.14 mm |
| April | 6 °C | 18.9 °C | 49.02 mm |
| May | 7.9 °C | 21.5 °C | 30.23 mm |
| June | 9.8 °C | 24.8 °C | 7.11 mm |
| July | 10.9 °C | 26.6 °C | 0.51 mm |
| August | 11.1 °C | 26.9 °C | 2.03 mm |
| September | 9.9 °C | 26.9 °C | 3.3 mm |
| October | 7.9 °C | 24.1 °C | 35.81 mm |
| November | 5 °C | 18.3 °C | 81.03 mm |
| December | 3.1 °C | 14 °C | 150.88 mm |
| Annual | 7 °C | 20.8 °C | 765.56 mm |
| 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 : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 9b : -3.9°C to -1.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |