Arnold, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 43.7 °F (low) to 66.7 °F (high). Annual precipitation averages 49.4 Inches. Arnold is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 33.7 °F | 51.1 °F | 9.17 in. |
| February | 33.4 °F | 52.0 °F | 8.5 in. |
| March | 35.2 °F | 55.9 °F | 7.42 in. |
| April | 38.1 °F | 60.1 °F | 4.26 in. |
| May | 44.5 °F | 68.9 °F | 2.6 in. |
| June | 52.0 °F | 78.9 °F | 0.65 in. |
| July | 58.8 °F | 86.9 °F | 0.09 in. |
| August | 58.5 °F | 87.0 °F | 0.26 in. |
| September | 53.9 °F | 81.4 °F | 0.46 in. |
| October | 45.9 °F | 70.1 °F | 2.68 in. |
| November | 37.9 °F | 58.0 °F | 4.55 in. |
| December | 33.0 °F | 49.7 °F | 8.71 in. |
| Annual | 43.7 °F | 66.7 °F | 49.35 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 8b : 15°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 8b : 15°F to 20°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |