Castle Rock, Colorado has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 34.7 °F (low) to 63.6 °F (high). Annual precipitation averages 18.1 Inches. Castle Rock is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 17.0 °F | 44.9 °F | 0.62 in. |
| February | 18.3 °F | 45.5 °F | 0.67 in. |
| March | 25.4 °F | 53.6 °F | 1.5 in. |
| April | 31.5 °F | 59.8 °F | 2.3 in. |
| May | 40.6 °F | 68.7 °F | 2.19 in. |
| June | 50.0 °F | 80.5 °F | 2.15 in. |
| July | 56.1 °F | 86.5 °F | 2.35 in. |
| August | 54.5 °F | 84.2 °F | 2.45 in. |
| September | 46.4 °F | 77.4 °F | 1.44 in. |
| October | 34.4 °F | 64.9 °F | 0.98 in. |
| November | 25.0 °F | 53.1 °F | 0.76 in. |
| December | 17.0 °F | 44.3 °F | 0.64 in. |
| Annual | 34.7 °F | 63.6 °F | 18.05 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |