Winchester, Ontario climate data is summarized below. Average annual temperatures range from 2 °C (low) to 12.5 °C (high). Annual precipitation averages 518 Millimeters. Winchester is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -13.14 °C | -4.05 °C | 0 mm |
| February | -12.93 °C | -3.33 °C | 0 mm |
| March | -6.5 °C | 3.71 °C | 19 mm |
| April | 1.38 °C | 12.65 °C | 46 mm |
| May | 7.84 °C | 20.41 °C | 57 mm |
| June | 12.97 °C | 24.65 °C | 69 mm |
| July | 15.46 °C | 27.29 °C | 94 mm |
| August | 14.52 °C | 26.34 °C | 85 mm |
| September | 9.74 °C | 21.81 °C | 60 mm |
| October | 4.42 °C | 14.25 °C | 53 mm |
| November | -1.56 °C | 7.08 °C | 26 mm |
| December | -8.42 °C | -1.18 °C | 9 mm |
| Annual | 2 °C | 12.5 °C | 518 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |