Graniteville, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5 °C (low) to 17.1 °C (high). Annual precipitation averages 1710.9 Millimeters. Graniteville is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -0.7 °C | 8.8 °C | 286 mm |
| February | -0.9 °C | 9.2 °C | 278.13 mm |
| March | -0.2 °C | 10.9 °C | 259.08 mm |
| April | 1.5 °C | 13.6 °C | 149.35 mm |
| May | 5.3 °C | 18.3 °C | 100.84 mm |
| June | 9.6 °C | 23.6 °C | 31.75 mm |
| July | 13.8 °C | 28.1 °C | 2.79 mm |
| August | 13.3 °C | 27.8 °C | 5.08 mm |
| September | 10.6 °C | 25.2 °C | 14.99 mm |
| October | 6.2 °C | 19.1 °C | 89.66 mm |
| November | 1.9 °C | 12.1 °C | 173.48 mm |
| December | -0.9 °C | 7.9 °C | 319.79 mm |
| Annual | 5 °C | 17.1 °C | 1710.94 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |