Graton, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 44.2 °F (low) to 70.9 °F (high). Annual precipitation averages 40.7 Inches. 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 | 37.8 °F | 57.6 °F | 7.9 in. |
| February | 39.1 °F | 61.2 °F | 7.76 in. |
| March | 40.9 °F | 64.3 °F | 5.4 in. |
| April | 42.5 °F | 68.4 °F | 2.62 in. |
| May | 46.0 °F | 73.6 °F | 1.43 in. |
| June | 49.4 °F | 79.6 °F | 0.39 in. |
| July | 51.3 °F | 81.7 °F | 0.02 in. |
| August | 51.4 °F | 82.2 °F | 0.11 in. |
| September | 49.3 °F | 82.3 °F | 0.17 in. |
| October | 45.5 °F | 76.8 °F | 1.97 in. |
| November | 40.5 °F | 65.5 °F | 4.36 in. |
| December | 37.2 °F | 57.5 °F | 8.52 in. |
| Annual | 44.2 °F | 70.9 °F | 40.65 in. |
| 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 : 20°F to 25°F |
| Plant Hardiness Zone - 2012 | Zone 9a : 20°F to 25°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |