Williamsburg, Ontario climate data is summarized below. Average annual temperatures range from 1.9 °C (low) to 12.5 °C (high). Annual precipitation averages 603 Millimeters. Williamsburg is located in USDA Plant Hardiness Zone 5a. 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 | -13.2 °C | -3.82 °C | 0 mm |
| February | -13.22 °C | -3.33 °C | 1 mm |
| March | -6.96 °C | 3.59 °C | 23 mm |
| April | 1.14 °C | 12.63 °C | 52 mm |
| May | 7.7 °C | 20.31 °C | 65 mm |
| June | 12.85 °C | 24.59 °C | 86 mm |
| July | 15.36 °C | 27.27 °C | 116 mm |
| August | 14.42 °C | 26.36 °C | 85 mm |
| September | 9.7 °C | 21.86 °C | 65 mm |
| October | 4.41 °C | 14.32 °C | 64 mm |
| November | -1.68 °C | 7.14 °C | 33 mm |
| December | -8.32 °C | -1.02 °C | 13 mm |
| Annual | 1.9 °C | 12.5 °C | 603 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 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |