Hamilton City, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 49.2 °F (low) to 74.9 °F (high). Annual precipitation averages 23 Inches. Hamilton City is located in USDA Plant Hardiness Zone 9b. The growing season typically runs from the last frost around Feb. 11 - Feb. 20 through the first frost around Dec. 11 - Dec. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 38.4 °F | 56.0 °F | 4.7 in. |
| February | 40.7 °F | 61.1 °F | 4.43 in. |
| March | 43.2 °F | 66.1 °F | 3.0 in. |
| April | 46.1 °F | 72.2 °F | 1.5 in. |
| May | 52.9 °F | 80.4 °F | 1.17 in. |
| June | 59.1 °F | 88.1 °F | 0.32 in. |
| July | 62.2 °F | 93.6 °F | 0.02 in. |
| August | 60.5 °F | 92.6 °F | 0.07 in. |
| September | 57.0 °F | 89.1 °F | 0.26 in. |
| October | 50.3 °F | 79.2 °F | 1.03 in. |
| November | 42.4 °F | 64.6 °F | 2.23 in. |
| December | 37.9 °F | 55.7 °F | 4.31 in. |
| Annual | 49.2 °F | 74.9 °F | 23.04 in. |
| Average First Frost Date | Dec. 11 - Dec. 20 |
| Average Last Frost Date | Feb. 11 - Feb. 20 |
| 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 | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |