Dorchester, Ontario climate data is summarized below. Average annual temperatures range from 38.9 °F (low) to 56.1 °F (high). Annual precipitation averages 17.7 Inches. 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 | -22.5 °F | -18.6 °F | 177.8 in. |
| February | -23.3 °F | -18.8 °F | 0 in. |
| March | -19.9 °F | -14.8 °F | 609.6 in. |
| April | -16.5 °F | -10.5 °F | 812.8 in. |
| May | -13.1 °F | -6.6 °F | 1244.6 in. |
| June | -10.3 °F | -4 °F | 1803.4 in. |
| July | -9 °F | -2.8 °F | 2006.6 in. |
| August | -9.4 °F | -3.2 °F | 2032 in. |
| September | -11.7 °F | -5.4 °F | 1346.2 in. |
| October | -14.6 °F | -9.4 °F | 762 in. |
| November | -17.6 °F | -13.3 °F | 431.8 in. |
| December | -20.1 °F | -16.8 °F | 203.2 in. |
| Annual | 38.9 °F | 56.1 °F | 17.72 in. |
| 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 : -5°F to 0°F |
| Current Drought Conditions | Normal |