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Frost dates for Ontario, Oregon

In a typical year, Ontario’s last spring frost lands around Apr 22 and the first fall frost around Oct 9, a growing season of about 170 days. These are odds drawn from 30-year NOAA climate normals, not a promise. USDA zone 7a.

Right now the typical frost season has arrived; planting waits for spring.

Last spring frost and first fall frost odds for Ontario, Oregon
OddsLast spring frostFirst fall frost
10 percentApr 7Sep 26
50 percentApr 22Oct 9
90 percentMay 7Oct 23

A 10 percent year is an early year, a 90 percent year a late one. Frost-sensitive planting usually waits for the 90 percent side of the last-frost band.

Soil in Ontario is typically around 49°F at 4 inches this time of year, estimated from the last two weeks of normal air temperatures.

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Common questions

When is the last frost in Ontario, Oregon?

Ontario’s last spring frost falls around April 22 in a typical year. One year in ten it is done by April 7, and one year in ten frost holds on until May 7. Frost-sensitive planting usually waits for the late side of that band.

When is the first fall frost in Ontario?

The first fall frost arrives around October 9 in a typical year, as early as September 26 in an early year and as late as October 23 in a late one.

How long is the growing season in Ontario?

About 170 days, counted between the typical last spring frost and the typical first fall frost.

What USDA zone is Ontario in?

Ontario is in USDA hardiness zone 7a under the 2023 USDA Plant Hardiness Zone Map.

Dates come from 30-year NOAA climate normals for the nearest reporting station. They describe odds, not a forecast.

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