Markham, Ontario climate data is summarized below. Average annual temperatures range from 3.7 °C (low) to 13.2 °C (high). Annual precipitation averages 932 Millimeters. 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 | -8.99 °C | -1.46 °C | 20 mm |
| February | -9.98 °C | -1.79 °C | 17 mm |
| March | -4.25 °C | 5.08 °C | 66 mm |
| April | 2.24 °C | 12.65 °C | 94 mm |
| May | 8.55 °C | 20.07 °C | 100 mm |
| June | 13.62 °C | 24.73 °C | 123 mm |
| July | 16.18 °C | 27.4 °C | 111 mm |
| August | 15.57 °C | 26.5 °C | 117 mm |
| September | 11.04 °C | 21.87 °C | 79 mm |
| October | 5.74 °C | 14.48 °C | 86 mm |
| November | 0.04 °C | 7.91 °C | 66 mm |
| December | -5.04 °C | 1.35 °C | 53 mm |
| Annual | 3.7 °C | 13.2 °C | 932 mm |
| 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 : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |