Newcastle, Wyoming has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 0.7 °C (low) to 14.9 °C (high). Annual precipitation averages 439.2 Millimeters. Newcastle is located in USDA Plant Hardiness Zone 5a. 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 | -10.8 °C | 1.6 °C | 12.45 mm |
| February | -9.9 °C | 2.9 °C | 16 mm |
| March | -4.9 °C | 8.7 °C | 20.57 mm |
| April | -0.7 °C | 13.6 °C | 44.45 mm |
| May | 4.9 °C | 18.8 °C | 75.44 mm |
| June | 10.2 °C | 25 °C | 70.1 mm |
| July | 13.9 °C | 30.2 °C | 61.47 mm |
| August | 12.8 °C | 29.6 °C | 50.8 mm |
| September | 7.6 °C | 23.9 °C | 28.7 mm |
| October | 0.7 °C | 15.3 °C | 32 mm |
| November | -5.6 °C | 7.7 °C | 14.22 mm |
| December | -10.4 °C | 1.7 °C | 12.95 mm |
| Annual | 0.7 °C | 14.9 °C | 439.15 mm |
| 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 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |