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Frost Dates for Boise, Idaho, United States of America

Coordinates: 43.614, -116.203

Growing Season

The last spring air frost in Boise, Idaho, United States of America typically occurs around May 18, and the first autumn air frost around Sep 15. This gives a frost-free growing season of approximately 120 days.

USDA Hardiness Zone

This location falls in USDA Hardiness Zone 6b, where the average annual extreme minimum temperature is -20.6 to -17.8°C (-5 to 0°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 -5°C (23°F). The warmest month is July, with an average high of 32°C (90°F).

Frost Risk Breakdown

Frost dates at three temperature thresholds: Air frost (0°C / 32°F): May 18 (last spring) to Sep 15 (first autumn). Light ground frost (-1°C / 30°F): May 4 (last spring) to Sep 24 (first autumn). Hard ground frost (-2°C / 28°F): Apr 11 (last spring) to Oct 10 (first autumn).

We predict your growing zone to be approximately ...

USDA Growing Zone: USDA Growing Zone - 6b

... 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 18 to Sep 15, which provides approximately 119 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 May 4 to Sep 24, which provides a total of 143 days for growing.

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