Granby, Colorado has a Subarctic With Cool Summers And Year Around Rainfall climate (Köppen classification: Dfc). Average annual temperatures range from -5.5 °C (low) to 12.2 °C (high). Annual precipitation averages 335.5 Millimeters. Granby is located in USDA Plant Hardiness Zone 4a. The growing season typically runs from the last frost around Jun. 1 - Jun. 10 through the first frost around Aug. 21 - Aug. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -17.3 °C | -1.9 °C | 20.32 mm |
| February | -15.5 °C | 0.4 °C | 20.57 mm |
| March | -10.1 °C | 6.1 °C | 21.34 mm |
| April | -5.4 °C | 11.2 °C | 28.96 mm |
| May | -1.2 °C | 16.8 °C | 39.37 mm |
| June | 2.4 °C | 22.8 °C | 27.69 mm |
| July | 5.8 °C | 26.2 °C | 35.81 mm |
| August | 4.8 °C | 25 °C | 37.85 mm |
| September | 0.8 °C | 21.2 °C | 35.81 mm |
| October | -4.4 °C | 13.9 °C | 28.7 mm |
| November | -10.1 °C | 5.6 °C | 19.56 mm |
| December | -15.9 °C | -1.3 °C | 19.56 mm |
| Annual | -5.5 °C | 12.2 °C | 335.54 mm |
| Average First Frost Date | Aug. 21 - Aug. 31 |
| Average Last Frost Date | Jun. 1 - Jun. 10 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 4a : -34.4°C to -31.7°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Dfc - Subarctic With Cool Summers And Year Around Rainfall |