Dorchester, Ontario climate data is summarized below. Average annual temperatures range from 3.8 °C (low) to 13.4 °C (high). Annual precipitation averages 450 Millimeters. Dorchester is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.51 °C | -1.42 °C | 7 mm |
| February | -9.87 °C | -1.81 °C | 0 mm |
| March | -3.79 °C | 5.33 °C | 24 mm |
| April | 2.23 °C | 13.14 °C | 32 mm |
| May | 8.43 °C | 20.2 °C | 49 mm |
| June | 13.54 °C | 24.88 °C | 71 mm |
| July | 15.78 °C | 26.96 °C | 79 mm |
| August | 15.16 °C | 26.18 °C | 80 mm |
| September | 11 °C | 22.2 °C | 53 mm |
| October | 5.77 °C | 15.16 °C | 30 mm |
| November | 0.3 °C | 8.1 °C | 17 mm |
| December | -4.25 °C | 1.68 °C | 8 mm |
| Annual | 3.8 °C | 13.4 °C | 450 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Normal |