Preston, Ontario climate data is summarized below. Average annual temperatures range from 3 °C (low) to 12.9 °C (high). Annual precipitation averages 874 Millimeters. Preston 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 | -9.26 °C | -1.96 °C | 11 mm |
| February | -10.69 °C | -2.28 °C | 14 mm |
| March | -4.82 °C | 4.92 °C | 52 mm |
| April | 1.46 °C | 12.5 °C | 82 mm |
| May | 7.78 °C | 19.61 °C | 101 mm |
| June | 12.89 °C | 24.22 °C | 116 mm |
| July | 14.96 °C | 26.69 °C | 133 mm |
| August | 14.31 °C | 25.79 °C | 108 mm |
| September | 10.24 °C | 21.6 °C | 91 mm |
| October | 5.13 °C | 14.6 °C | 75 mm |
| November | -0.46 °C | 7.66 °C | 50 mm |
| December | -5.24 °C | 1.06 °C | 41 mm |
| Annual | 3 °C | 12.9 °C | 874 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 |
| Current Drought Conditions | Normal |