Frost Dates for Markham, Ontario, Canada

Coordinates: 43.867, -79.267

Growing Season

The last spring air frost in Markham, Ontario, Canada typically occurs around May 7, and the first autumn air frost around Sep 25. This gives a frost-free growing season of approximately 141 days.

USDA Hardiness Zone

This location falls in USDA Hardiness Zone 5b, where the average annual extreme minimum temperature is -26.1 to -23.3°C (-15 to -10°F). This zone rating helps gardeners determine which perennial plants are likely to survive winter.

Temperature Overview

The coldest month is January, with an average low of -9°C (16°F). The warmest month is July, with an average high of 26°C (79°F).

Frost Risk Breakdown

Frost dates at three temperature thresholds: Air frost (0°C / 32°F): May 7 (last spring) to Sep 25 (first autumn). Light ground frost (-1°C / 30°F): Apr 27 (last spring) to Oct 4 (first autumn). Hard ground frost (-2°C / 28°F): Apr 12 (last spring) to Oct 19 (first autumn).

We predict your growing zone to be approximately ...

USDA Growing Zone: USDA Growing Zone - 5b

... and the frost data for your area is ...

Current Risk Level: Hard Ground Frost possible

for today based on past data only.

We predict a frost free growing season at your location from May 7 to Sep 25, which provides approximately 140 frost free days.

For the less tender plants, or if you are planning to protect your plants with fleece etc, your growing season could stretch from Apr 27 to Oct 4, which provides a total of 160 days for growing.

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