Onyx, California has a Hot Desert Climate climate (Köppen classification: BWh). Average annual temperatures range from 8.6 °C (low) to 24.4 °C (high). Annual precipitation averages 267.2 Millimeters. Onyx is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.3 °C | 14.5 °C | 67.56 mm |
| February | 2.1 °C | 15.7 °C | 65.28 mm |
| March | 3.9 °C | 18.5 °C | 32 mm |
| April | 6.3 °C | 21.5 °C | 15.24 mm |
| May | 10.6 °C | 26.4 °C | 5.84 mm |
| June | 15 °C | 32.1 °C | 2.79 mm |
| July | 18.1 °C | 36.2 °C | 3.81 mm |
| August | 17.3 °C | 36.2 °C | 5.59 mm |
| September | 14.6 °C | 32.7 °C | 3.3 mm |
| October | 8.9 °C | 26.1 °C | 12.95 mm |
| November | 3.9 °C | 19.1 °C | 18.03 mm |
| December | 0.8 °C | 13.9 °C | 34.8 mm |
| Annual | 8.6 °C | 24.4 °C | 267.19 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 9a : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | BWh - Hot Desert Climate |