Frost Dates for 97140 — Sherwood, Oregon

Half of springs at Rex 1 S, OR see their last 32°F night by March 21; only one in ten is past it by February 23, and one in ten still has one after April 19. Planting tender crops after April 2 leaves a 30% risk of a frost on them, after April 10 20%, and after April 19 10%. The 29 days between the even-odds date and the one-in-ten date is wider than at 82% 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 22 in half of years, as early as November 4 one year in ten, and holds off past December 12 one year in ten. A hard freeze of 28°F follows 18 days later, around December 10; in spring the one-in-ten date for 28°F is March 11, 39 days before the 32°F one. The freeze-free season lasts 241 days in a typical year, longer than at 78% of the 103 Oregon stations; it reaches 275 days one year in ten and falls short of 211 one year in ten. On average 43 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 31 days longer, to about April 21, and return around November 3. Nights of 24°F, cold enough to damage hardier plants, come in 70% of winters and 16°F in 8%.

August is the warmest month at Rex 1 S, OR, averaging 81°F by day and 56°F at night; December is the coldest at 44°F and 34°F. A freezing night is all but certain in every month from December to February (a 90% chance or more). From May to October the chance of a 32°F night stays under 10% each month. In spring, March still brings one in 71% of years and April still brings one in 33% of years.

Warmth for growing adds up to 2,381 growing degree days a year (base 50°F), more than at 63% of the 103 Oregon stations. 29% of them (680) have built up by the end of June, and August adds the most, 575. Precipitation totals 44.5 inches a year, most in December (7.4") and least in July (0.4"); May to September bring 15% of it.

The nearest other station, N Willamette Exp Stn, OR, 7 miles southeast of Sherwood and 365 feet lower, has a last frost 3 days earlier (March 18), a first frost 9 days earlier (November 13), a season 2 days longer.

Measurable snow is rare here: only 10 of 27 winters from 1991 to 2020 recorded 0.1 inch or more at Rex 1 S, OR, 4.4 miles away, so there is no typical first-snow date to plan around.

ZIP 97140 is 4 miles from Rex 1 S, OR, which stands at 515 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 97132 (Newberg). The 2023 USDA Plant Hardiness Zone Map lists ZIP 97140 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.