Arnold, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 6.5 °C (low) to 19.3 °C (high). Annual precipitation averages 1253.5 Millimeters. 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 | 0.9 °C | 10.6 °C | 232.92 mm |
| February | 0.8 °C | 11.1 °C | 215.9 mm |
| March | 1.8 °C | 13.3 °C | 188.47 mm |
| April | 3.4 °C | 15.6 °C | 108.2 mm |
| May | 6.9 °C | 20.5 °C | 66.04 mm |
| June | 11.1 °C | 26.1 °C | 16.51 mm |
| July | 14.9 °C | 30.5 °C | 2.29 mm |
| August | 14.7 °C | 30.6 °C | 6.6 mm |
| September | 12.2 °C | 27.4 °C | 11.68 mm |
| October | 7.7 °C | 21.2 °C | 68.07 mm |
| November | 3.3 °C | 14.4 °C | 115.57 mm |
| December | 0.6 °C | 9.8 °C | 221.23 mm |
| Annual | 6.5 °C | 19.3 °C | 1253.48 mm |
| 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 : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |