Frost Dates for 97071 — Woodburn, Oregon

Half of springs at Aurora State Airport, OR see their last 32°F night by March 16; only one in ten is past it by February 21, and one in ten still has one after April 7. Planting tender crops after March 25 leaves a 30% risk of a frost on them, after March 31 20%, and after April 7 10%. The 22 days between the even-odds date and the one-in-ten date is narrower than at 45% of the 103 Oregon stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.

In fall the first 32°F night comes by November 14 in half of years, as early as October 27 one year in ten, and holds off past December 6 one year in ten. A hard freeze of 28°F follows 17 days later, around December 1; in spring the one-in-ten date for 28°F is March 8, 30 days before the 32°F one. The freeze-free season lasts 242 days in a typical year, longer than at 79% of the 103 Oregon stations; it reaches 276 days one year in ten and falls short of 215 one year in ten. On average 39 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 30 days longer, to about April 15, and return around October 26. Nights of 24°F, cold enough to damage hardier plants, come in 76% of winters and 16°F in 7%.

August is the warmest month at Aurora State Airport, OR, averaging 83°F by day and 56°F at night; December is the coldest at 48°F and 36°F. A freezing night is all but certain in every month from December to February (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, March still brings one in 73% of years and April still brings one in 19% of years.

Warmth for growing adds up to 2,707 growing degree days a year (base 50°F), more than at 78% of the 103 Oregon stations. 31% of them (833) have built up by the end of June, and August adds the most, 614. Precipitation totals 39.6 inches a year, most in December (6.2") and least in July (0.4"); May to September bring 17% of it.

The nearest other station, Silverton, OR, 10 miles south of Woodburn and 212 feet higher, has a last frost 12 days later (March 28), a first frost 4 days earlier (November 10), a season 15 days shorter.

Measurable snow is rare here: only 12 of 27 winters from 1991 to 2020 recorded 0.1 inch or more at Silverton, OR, 10.2 miles away, so there is no typical first-snow date to plan around.

ZIP 97071 is 8 miles from Aurora State Airport, OR, which stands at 196 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 97071 in zone 8b, the band where the coldest night of the year averaged 15 to 20°F (-9.4 to -6.7°C) over 1991–2020; a zone describes winter lows, not frost dates.