Frost Dates for Ottawa, Ontario, Canada

Coordinates: 45.417, -75.700

Growing Season

The last spring air frost in Ottawa, Ontario, Canada typically occurs around May 10, and the first autumn air frost around Sep 17. This gives a frost-free growing season of approximately 130 days.

USDA Hardiness Zone

This location falls in USDA Hardiness Zone 4b, where the average annual extreme minimum temperature is -31.7 to -28.9°C (-25 to -20°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 -14°C (7°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 10 (last spring) to Sep 17 (first autumn). Light ground frost (-1°C / 30°F): Apr 29 (last spring) to Sep 27 (first autumn). Hard ground frost (-2°C / 28°F): Apr 14 (last spring) to Oct 12 (first autumn).

We predict your growing zone to be approximately ...

USDA Growing Zone: USDA Growing Zone - 4b

... 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 10 to Sep 17, which provides approximately 129 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 29 to Sep 27, which provides a total of 151 days for growing.

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