Hercules, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 49.6 °F (low) to 68.3 °F (high). Annual precipitation averages 19.6 Inches. Hercules is located in USDA Plant Hardiness Zone 9b.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 42.5 °F | 56.0 °F | 3.78 in. |
| February | 43.8 °F | 60.1 °F | 4.11 in. |
| March | 46.1 °F | 64.0 °F | 2.66 in. |
| April | 48.1 °F | 67.3 °F | 1.3 in. |
| May | 51.5 °F | 71.0 °F | 0.61 in. |
| June | 54.3 °F | 75.1 °F | 0.16 in. |
| July | 56.1 °F | 77.1 °F | 0.0 in. |
| August | 56.4 °F | 77.1 °F | 0.04 in. |
| September | 55.6 °F | 77.7 °F | 0.07 in. |
| October | 52.3 °F | 73.4 °F | 0.84 in. |
| November | 46.5 °F | 64.1 °F | 2.02 in. |
| December | 42.5 °F | 56.4 °F | 3.97 in. |
| Annual | 49.6 °F | 68.3 °F | 19.56 in. |
| Average First Frost Date | No Frost |
| Average Last Frost Date | |
| Average Days With Frost | Frost Free |
| Plant Hardiness Zone | Zone 9b : 25°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 9b : 25°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |