Markham, Ontario climate data is summarized below. Average annual temperatures range from 38.7 °F (low) to 55.8 °F (high). Annual precipitation averages 36.7 Inches. Markham is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -22.8 °F | -18.6 °F | 508 in. |
| February | -23.3 °F | -18.8 °F | 431.8 in. |
| March | -20.1 °F | -15 °F | 1676.4 in. |
| April | -16.5 °F | -10.8 °F | 2387.6 in. |
| May | -13 °F | -6.6 °F | 2540 in. |
| June | -10.2 °F | -4 °F | 3124.2 in. |
| July | -8.8 °F | -2.6 °F | 2819.4 in. |
| August | -9.1 °F | -3.1 °F | 2971.8 in. |
| September | -11.6 °F | -5.6 °F | 2006.6 in. |
| October | -14.6 °F | -9.7 °F | 2184.4 in. |
| November | -17.8 °F | -13.4 °F | 1676.4 in. |
| December | -20.6 °F | -17 °F | 1346.2 in. |
| Annual | 38.7 °F | 55.8 °F | 36.71 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |