Last frost date in Hillsboro, Oregon

April 16

Average last frost in spring. In an early year (1 in 10) it's over by March 25; in a late year (1 in 10) it comes after May 3.

October 23

Average first frost in fall. 1 year in 10 it comes by October 3.

Source: NOAA U.S. Climate Normals 1991–2020, station Portland-hillsboro AP (USW00094261), 1.1 miles from Hillsboro, elevation 204 ft. NOAA National Centers for Environmental Information. These are long-term averages, not a forecast.

What to plant now

Frost dates for Hillsboro, Oregon
Early yearAverageLate year
Last frost in springMar 25Apr 16May 3
First frost in fallOct 3Oct 23Nov 18

An early or late year is one in 10: 1 year in 10 the frost comes before the early date, and 1 year in 10 after the late date.

Frost-free days in an average year: 191

Planting calendar for Hillsboro

Fall planting

USDA dates for places whose average first freeze is about October 20 (Hillsboro: October 23).

USDA lists chervil and chives, garlic, horseradish, leeks, onion plants, onion seed, onion sets, parsnips, garden peas, shallots as generally spring-planted here.

Spring planting

USDA dates for places whose average last freeze is about April 20 (Hillsboro: April 16).

USDA lists chinese cabbage as generally fall-planted here.

Planting dates: USDA Home and Garden Bulletin No. 9 (1967), “Suburban and Farm Vegetable Gardens,” tables 4 and 5 (earliest safe spring and latest safe fall dates), applied to this place's NOAA frost dates. “Plants” means setting out transplants, not sowing seed. How we match the table.

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