Guerneville, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 44.4 °F (low) to 69.7 °F (high). Annual precipitation averages 48.7 Inches. 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 | 38.5 °F | 57.4 °F | 9.11 in. |
| February | 39.6 °F | 60.8 °F | 9.29 in. |
| March | 41.3 °F | 63.6 °F | 6.68 in. |
| April | 42.8 °F | 67.3 °F | 3.23 in. |
| May | 45.9 °F | 72.5 °F | 1.87 in. |
| June | 49.0 °F | 77.8 °F | 0.24 in. |
| July | 50.8 °F | 79.0 °F | 0.05 in. |
| August | 51.2 °F | 80.7 °F | 0.07 in. |
| September | 49.1 °F | 79.4 °F | 0.14 in. |
| October | 45.7 °F | 75.0 °F | 2.1 in. |
| November | 41.0 °F | 65.1 °F | 4.85 in. |
| December | 37.7 °F | 57.5 °F | 11.04 in. |
| Annual | 44.4 °F | 69.7 °F | 48.67 in. |
| 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 : 25°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 9b : 25°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |