Frost Dates for 98250 — Friday Harbor, Washington

Half of springs at Friday Harbor Airport, WA see their last 32°F night by March 26; only one in ten is past it by February 25, and one in ten still has one after April 21. Planting tender crops after April 4 leaves a 30% risk of a frost on them, after April 10 20%, and after April 21 10%. The 26 days between the even-odds date and the one-in-ten date is wider than at 89% of the 113 Washington 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 10 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 21 days later, around December 1; in spring the one-in-ten date for 28°F is March 18, 34 days before the 32°F one. The freeze-free season lasts 230 days in a typical year, longer than at 82% of the 113 Washington stations; it reaches 265 days one year in ten and falls short of 197 one year in ten. On average 40 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 34 days longer, to about April 29, and return around October 24. Nights of 24°F, cold enough to damage hardier plants, come in 78% of winters and 16°F in 14%.

August is the warmest month at Friday Harbor Airport, WA, averaging 73°F by day and 50°F at night; December is the coldest at 46°F and 37°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 77% of years and April still brings one in 35% of years.

Warmth for growing adds up to 1,470 growing degree days a year (base 50°F), fewer than at 90% of the 113 Washington stations. 29% of them (431) have built up by the end of June, and August adds the most, 361. Precipitation totals 18.5 inches a year, most in November (3.0") and least in July (0.5"); May to September bring 22% of it.

The nearest other station, Olga 2 SE, WA, 13 miles east of Friday Harbor, has a last frost 28 days earlier (February 26), a first frost 19 days later (November 29), a season 46 days longer.

Measurable snow is rare here: only 6 of 18 winters from 1991 to 2020 recorded 0.1 inch or more at Anacortes, WA, 21.3 miles away, so there is no typical first-snow date to plan around.

ZIP 98250 is 3 miles from Friday Harbor Airport, WA, which stands at 109 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 98250 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.