Frost Dates for Portland, Oregon, United States of America

Coordinates: 45.524, -122.675

Growing Season

The last spring air frost in Portland, Oregon, United States of America typically occurs around May 20, and the first autumn air frost around Sep 30. This gives a frost-free growing season of approximately 133 days.

USDA Hardiness Zone

This location falls in USDA Hardiness Zone 8b, where the average annual extreme minimum temperature is -9.4 to -6.7°C (15 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 2°C (36°F). The warmest month is August, with an average high of 29°C (84°F).

Frost Risk Breakdown

Frost dates at three temperature thresholds: Air frost (0°C / 32°F): May 20 (last spring) to Sep 30 (first autumn). Light ground frost (-1°C / 30°F): Apr 27 (last spring) to Oct 17 (first autumn). Hard ground frost (-2°C / 28°F): Mar 11 (last spring) to Nov 18 (first autumn).

We predict your growing zone to be approximately ...

USDA Growing Zone: USDA Growing Zone - 8b

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

Current Risk Level: Light Ground Frost possible

for today based on past data only.

We predict a frost free growing season at your location from May 20 to Sep 30, which provides approximately 132 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 17, which provides a total of 173 days for growing.

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