Clayton, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 47.5 °F (low) to 71.4 °F (high). Annual precipitation averages 19.5 Inches. Clayton 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. 11 - Dec. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 39.2 °F | 56.0 °F | 3.86 in. |
| February | 40.9 °F | 60.1 °F | 3.78 in. |
| March | 42.8 °F | 64.5 °F | 2.64 in. |
| April | 45.4 °F | 69.2 °F | 1.54 in. |
| May | 49.7 °F | 74.1 °F | 0.67 in. |
| June | 53.5 °F | 81.4 °F | 0.14 in. |
| July | 56.0 °F | 86.0 °F | 0.01 in. |
| August | 56.4 °F | 86.0 °F | 0.03 in. |
| September | 54.7 °F | 84.1 °F | 0.08 in. |
| October | 49.9 °F | 75.4 °F | 0.91 in. |
| November | 42.9 °F | 64.2 °F | 1.95 in. |
| December | 38.9 °F | 56.0 °F | 3.87 in. |
| Annual | 47.5 °F | 71.4 °F | 19.48 in. |
| Average First Frost Date | Dec. 11 - Dec. 20 |
| Average Last Frost Date | Feb. 21 - Feb. 29 |
| Average Days With Frost | 10-20 Days |
| Plant Hardiness Zone | Zone 9b : 25°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 9a : 20°F to 25°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |