Graton, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.8 °C (low) to 21.6 °C (high). Annual precipitation averages 1032.5 Millimeters. Graton is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 3.2 °C | 14.2 °C | 200.66 mm |
| February | 3.9 °C | 16.2 °C | 197.1 mm |
| March | 4.9 °C | 17.9 °C | 137.16 mm |
| April | 5.8 °C | 20.2 °C | 66.55 mm |
| May | 7.8 °C | 23.1 °C | 36.32 mm |
| June | 9.7 °C | 26.4 °C | 9.91 mm |
| July | 10.7 °C | 27.6 °C | 0.51 mm |
| August | 10.8 °C | 27.9 °C | 2.79 mm |
| September | 9.6 °C | 27.9 °C | 4.32 mm |
| October | 7.5 °C | 24.9 °C | 50.04 mm |
| November | 4.7 °C | 18.6 °C | 110.74 mm |
| December | 2.9 °C | 14.2 °C | 216.41 mm |
| Annual | 6.8 °C | 21.6 °C | 1032.51 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 40-50 Days |
| Plant Hardiness Zone | Zone 9a : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 9a : -6.7°C to -3.9°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |