Guerneville, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.9 °C (low) to 20.9 °C (high). Annual precipitation averages 1236.2 Millimeters. Guerneville is located in USDA Plant Hardiness Zone 9b. The growing season typically runs from the last frost around Feb. 21 - Feb. 29 through the first frost around Dec. 1 - Dec. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 3.6 °C | 14.1 °C | 231.39 mm |
| February | 4.2 °C | 16 °C | 235.97 mm |
| March | 5.2 °C | 17.6 °C | 169.67 mm |
| April | 6 °C | 19.6 °C | 82.04 mm |
| May | 7.7 °C | 22.5 °C | 47.5 mm |
| June | 9.4 °C | 25.4 °C | 6.1 mm |
| July | 10.4 °C | 26.1 °C | 1.27 mm |
| August | 10.7 °C | 27.1 °C | 1.78 mm |
| September | 9.5 °C | 26.3 °C | 3.56 mm |
| October | 7.6 °C | 23.9 °C | 53.34 mm |
| November | 5 °C | 18.4 °C | 123.19 mm |
| December | 3.2 °C | 14.2 °C | 280.42 mm |
| Annual | 6.9 °C | 20.9 °C | 1236.23 mm |
| Average First Frost Date | Dec. 1 - Dec. 10 |
| Average Last Frost Date | Feb. 21 - Feb. 29 |
| Average Days With Frost | 20-30 Days |
| Plant Hardiness Zone | Zone 9b : -3.9°C to -1.1°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 |