Hamilton City, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 9.6 °C (low) to 23.8 °C (high). Annual precipitation averages 585.2 Millimeters. 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 | 3.6 °C | 13.3 °C | 119.38 mm |
| February | 4.8 °C | 16.2 °C | 112.52 mm |
| March | 6.2 °C | 18.9 °C | 76.2 mm |
| April | 7.8 °C | 22.3 °C | 38.1 mm |
| May | 11.6 °C | 26.9 °C | 29.72 mm |
| June | 15.1 °C | 31.2 °C | 8.13 mm |
| July | 16.8 °C | 34.2 °C | 0.51 mm |
| August | 15.8 °C | 33.7 °C | 1.78 mm |
| September | 13.9 °C | 31.7 °C | 6.6 mm |
| October | 10.2 °C | 26.2 °C | 26.16 mm |
| November | 5.8 °C | 18.1 °C | 56.64 mm |
| December | 3.3 °C | 13.2 °C | 109.47 mm |
| Annual | 9.6 °C | 23.8 °C | 585.21 mm |
| 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 : -3.9°C to -1.1°C |
| Plant Hardiness Zone - 2012 | Zone 9a : -6.7°C to -3.9°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |