Petaluma, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 7.2 °C (low) to 20.7 °C (high). Annual precipitation averages 701.8 Millimeters. Petaluma is located in USDA Plant Hardiness Zone 9a. 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 | 3.5 °C | 13.7 °C | 150.37 mm |
| February | 4.4 °C | 15.8 °C | 156.72 mm |
| March | 5.3 °C | 17.7 °C | 83.57 mm |
| April | 6.2 °C | 18.9 °C | 40.64 mm |
| May | 8.1 °C | 21.5 °C | 21.84 mm |
| June | 9.9 °C | 24.8 °C | 7.37 mm |
| July | 11.1 °C | 26.5 °C | 0.25 mm |
| August | 11.3 °C | 26.7 °C | 1.52 mm |
| September | 10.1 °C | 26.8 °C | 2.03 mm |
| October | 8 °C | 24 °C | 27.69 mm |
| November | 5.2 °C | 18.2 °C | 62.23 mm |
| December | 3.3 °C | 13.8 °C | 147.57 mm |
| Annual | 7.2 °C | 20.7 °C | 701.8 mm |
| Average First Frost Date | Dec. 1 - Dec. 10 |
| Average Last Frost Date | Feb. 21 - Feb. 29 |
| 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 |