Castle Valley, Utah has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 5.1 °C (low) to 20.5 °C (high). Annual precipitation averages 289.8 Millimeters. Castle Valley is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.9 °C | 5 °C | 19.56 mm |
| February | -3.7 °C | 9.2 °C | 19.81 mm |
| March | 0.7 °C | 15.5 °C | 23.62 mm |
| April | 3.9 °C | 19.8 °C | 28.7 mm |
| May | 9.1 °C | 25.6 °C | 24.64 mm |
| June | 14.6 °C | 32.5 °C | 10.92 mm |
| July | 18 °C | 35.7 °C | 20.57 mm |
| August | 16.7 °C | 34.2 °C | 29.72 mm |
| September | 12.3 °C | 29.1 °C | 33.02 mm |
| October | 4.6 °C | 21 °C | 35.31 mm |
| November | -1.3 °C | 12.6 °C | 21.59 mm |
| December | -6.9 °C | 5.3 °C | 22.35 mm |
| Annual | 5.1 °C | 20.5 °C | 289.81 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |