Westminster, Colorado has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 3 °C (low) to 18.6 °C (high). Annual precipitation averages 404.9 Millimeters. Westminster is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.9 °C | 7.9 °C | 11.94 mm |
| February | -6.2 °C | 8.4 °C | 14.73 mm |
| March | -2.1 °C | 13.3 °C | 32.77 mm |
| April | 1.4 °C | 16.7 °C | 56.13 mm |
| May | 6.5 °C | 21.6 °C | 67.56 mm |
| June | 11.7 °C | 28.3 °C | 43.43 mm |
| July | 15.1 °C | 31.8 °C | 43.94 mm |
| August | 14 °C | 30.5 °C | 42.67 mm |
| September | 9.3 °C | 26.2 °C | 29.46 mm |
| October | 2.6 °C | 18.9 °C | 30.23 mm |
| November | -2.8 °C | 12.3 °C | 20.57 mm |
| December | -7 °C | 7.5 °C | 11.43 mm |
| Annual | 3 °C | 18.6 °C | 404.86 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |