Frost Dates for 98239 — Coupeville, Washington

Half of springs at Coupeville 1 S, WA see their last 32°F night by March 17; only one in ten is past it by February 24, and one in ten still has one after April 3. Planting tender crops after March 26 leaves a 30% risk of a frost on them, after March 30 20%, and after April 3 10%. The 17 days between the even-odds date and the one-in-ten date is narrower than at 66% of the 113 Washington stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 11 in half of years, as early as October 21 one year in ten, and holds off past December 1 one year in ten. A hard freeze of 28°F follows 17 days later, around November 28; in spring the one-in-ten date for 28°F is March 12, 22 days before the 32°F one. The freeze-free season lasts 237 days in a typical year, longer than at 86% of the 113 Washington stations; it reaches 266 days one year in ten and falls short of 212 one year in ten. On average 32 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 27 days longer, to about April 13, and return around October 27. Nights of 24°F, cold enough to damage hardier plants, come in 84% of winters and 16°F in 12%.

August is the warmest month at Coupeville 1 S, WA, averaging 71°F by day and 53°F at night; December is the coldest at 44°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 80% of years and April still brings one in 15% of years.

Warmth for growing adds up to 1,420 growing degree days a year (base 50°F), fewer than at 95% of the 113 Washington stations. 29% of them (407) have built up by the end of June, and August adds the most, 360. Precipitation totals 21.8 inches a year, most in November (3.1") and least in August (0.7"); May to September bring 26% of it.

The nearest other station, Port Townsend, WA, 7 miles southwest of Coupeville, has a last frost 16 days earlier (March 1), a first frost 17 days later (November 28), a season 37 days longer.

Measurable snow is rare here: only 5 of 19 winters from 1991 to 2020 recorded 0.1 inch or more at Coupeville 1 S, WA, 1.1 miles away, so there is no typical first-snow date to plan around.

ZIP 98239 is 1 mile from Coupeville 1 S, WA, which stands at 50 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 98282 (Camano Island). The 2023 USDA Plant Hardiness Zone Map lists ZIP 98239 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.