New Castle, Colorado has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 31.8 °F (low) to 62.3 °F (high). Annual precipitation averages 14.9 Inches. New Castle is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 12.0 °F | 36.9 °F | 1.11 in. |
| February | 17.5 °F | 42.5 °F | 1.13 in. |
| March | 24.8 °F | 53.3 °F | 1.14 in. |
| April | 30.7 °F | 60.6 °F | 1.54 in. |
| May | 38.0 °F | 70.4 °F | 1.6 in. |
| June | 45.7 °F | 82.2 °F | 0.81 in. |
| July | 52.8 °F | 88.2 °F | 1.05 in. |
| August | 51.1 °F | 85.5 °F | 1.14 in. |
| September | 42.4 °F | 77.4 °F | 1.66 in. |
| October | 31.4 °F | 64.2 °F | 1.64 in. |
| November | 21.8 °F | 49.8 °F | 1.09 in. |
| December | 12.8 °F | 37.0 °F | 0.96 in. |
| Annual | 31.8 °F | 62.3 °F | 14.87 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Exceptional Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |