South Royalton, Vermont has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 0.8 °C (low) to 13.6 °C (high). Annual precipitation averages 1049.5 Millimeters. South Royalton 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 Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -13.4 °C | -1.8 °C | 72.64 mm |
| February | -12.7 °C | 0.3 °C | 59.94 mm |
| March | -7.4 °C | 5.1 °C | 75.18 mm |
| April | -0.7 °C | 12.9 °C | 80.77 mm |
| May | 5.9 °C | 20.4 °C | 85.85 mm |
| June | 10.9 °C | 25 °C | 109.73 mm |
| July | 13.9 °C | 27.7 °C | 113.28 mm |
| August | 12.9 °C | 26.5 °C | 97.79 mm |
| September | 8.9 °C | 22.7 °C | 86.36 mm |
| October | 2.6 °C | 15.1 °C | 101.85 mm |
| November | -2.7 °C | 7.8 °C | 77.72 mm |
| December | -8.5 °C | 1.1 °C | 88.39 mm |
| Annual | 0.8 °C | 13.6 °C | 1049.5 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| 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 | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |