Eureka, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 46.5 °F (low) to 58.2 °F (high). Annual precipitation averages 43.7 Inches. Eureka is located in USDA Plant Hardiness Zone 9b.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 42.2 °F | 55.0 °F | 7.99 in. |
| February | 42.4 °F | 55.3 °F | 6.15 in. |
| March | 42.9 °F | 56.0 °F | 6.28 in. |
| April | 44.6 °F | 56.2 °F | 4.02 in. |
| May | 47.6 °F | 57.9 °F | 1.71 in. |
| June | 50.0 °F | 59.7 °F | 0.83 in. |
| July | 52.3 °F | 60.7 °F | 0.25 in. |
| August | 52.9 °F | 62.1 °F | 0.17 in. |
| September | 50.6 °F | 62.0 °F | 0.57 in. |
| October | 47.2 °F | 60.5 °F | 2.22 in. |
| November | 44.2 °F | 58.0 °F | 4.99 in. |
| December | 41.5 °F | 54.8 °F | 8.56 in. |
| Annual | 46.5 °F | 58.2 °F | 43.74 in. |
| Average First Frost Date | Frost Rare |
| Average Last Frost Date | |
| Average Days With Frost | Frost Rare |
| Plant Hardiness Zone | Zone 9b : 25°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 9b : 25°F to 20°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |