Frost Dates for 97431 — Dexter, Oregon

Half of springs at Lookout Pt Dam, OR see their last 32°F night by March 7; only one in ten is past it by February 4, and one in ten still has one after April 2. Planting tender crops after March 18 leaves a 30% risk of a frost on them, after March 25 20%, and after April 2 10%. The 26 days between the even-odds date and the one-in-ten date is wider than at 72% 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 27 in half of years, as early as November 1 one year in ten, and holds off past December 21 one year in ten. A hard freeze of 28°F follows 19 days later, around December 16; in spring the one-in-ten date for 28°F is March 5, 28 days before the 32°F one. The freeze-free season lasts 263 days in a typical year, longer than at 91% of the 103 Oregon stations; it reaches 305 days one year in ten and falls short of 228 one year in ten. On average 27 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 40 days longer, to about April 16, and return around November 9. Nights of 24°F, cold enough to damage hardier plants, come in 50% of winters and 16°F in 5%.

July is the warmest month at Lookout Pt Dam, OR, averaging 80°F by day and 55°F at night; December is the coldest at 46°F and 37°F. A freezing night is all but certain in December (a 90% chance or more). From May to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 79% of years and March still brings one in 55% of years and April still brings one in 11% of years.

Warmth for growing adds up to 2,311 growing degree days a year (base 50°F), more than at 57% of the 103 Oregon stations. 27% of them (635) have built up by the end of June, and July adds the most, 535. Precipitation totals 45.9 inches a year, most in December (7.0") and least in July (0.5"); May to September bring 18% of it.

The nearest other station, Cottage Grove 2E, OR, 12 miles southwest of Dexter, has a last frost 48 days later (April 24), a first frost 33 days earlier (October 25), a season 80 days shorter.

Measurable snow is rare here: only 7 of 27 winters from 1991 to 2020 recorded 0.1 inch or more at Lookout Pt Dam, OR, 3.3 miles away, so there is no typical first-snow date to plan around.

ZIP 97431 is 3 miles from Lookout Pt Dam, OR, which stands at 712 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 97455 (Pleasant Hill). The 2023 USDA Plant Hardiness Zone Map lists ZIP 97431 in zone 9a, the band where the coldest night of the year averaged 20 to 25°F (-6.7 to -3.9°C) over 1991–2020; a zone describes winter lows, not frost dates.