Newcastle, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 48.9 °F (low) to 73.3 °F (high). Annual precipitation averages 27 Inches. Newcastle 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. 1 - Dec. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 38.6 °F | 55.2 °F | 4.89 in. |
| February | 40.2 °F | 59.3 °F | 4.58 in. |
| March | 42.9 °F | 63.7 °F | 4.05 in. |
| April | 45.1 °F | 68.5 °F | 2.3 in. |
| May | 50.8 °F | 77.3 °F | 1.46 in. |
| June | 56.8 °F | 86.5 °F | 0.38 in. |
| July | 61.6 °F | 93.7 °F | 0.0 in. |
| August | 61.2 °F | 92.5 °F | 0.03 in. |
| September | 57.4 °F | 87.3 °F | 0.2 in. |
| October | 50.6 °F | 76.8 °F | 1.41 in. |
| November | 43.1 °F | 63.5 °F | 2.83 in. |
| December | 37.9 °F | 54.9 °F | 4.88 in. |
| Annual | 48.9 °F | 73.3 °F | 27.01 in. |
| Average First Frost Date | Dec. 1 - Dec. 10 |
| 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 9b : 25°F to 20°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |