Frost Dates for 98020 — Edmonds, Washington

Half of springs at Everett Snohomish Airport, WA see their last 32°F night by March 9; only one in ten is past it by February 15, and one in ten still has one after March 29. Planting tender crops after March 17 leaves a 30% risk of a frost on them, after March 22 20%, and after March 29 10%. The 20 days between the even-odds date and the one-in-ten date is wider than at 52% of the 113 Washington stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 17 in half of years, as early as October 31 one year in ten, and holds off past December 7 one year in ten. A hard freeze of 28°F follows 19 days later, around December 6; in spring the one-in-ten date for 28°F is March 9, 20 days before the 32°F one. The freeze-free season lasts 250 days in a typical year, longer than at 92% of the 113 Washington stations; it reaches 285 days one year in ten and falls short of 224 one year in ten. On average 29 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 25 days longer, to about April 3, and return around November 2. Nights of 24°F, cold enough to damage hardier plants, come in 74% of winters and 16°F in 12%.

August is the warmest month at Everett Snohomish Airport, WA, averaging 73°F by day and 55°F at night; December is the coldest at 45°F and 36°F. A freezing night is all but certain in every month from December to January (a 90% chance or more). From April to September the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 89% of years and March still brings one in 71% of years.

Warmth for growing adds up to 1,771 growing degree days a year (base 50°F), fewer than at 67% of the 113 Washington stations. 28% of them (503) have built up by the end of June, and August adds the most, 440. Precipitation totals 33.4 inches a year, most in November (5.0") and least in July (0.8"); May to September bring 22% of it.

The nearest other station, Seattle Sand Pt Wsfo, WA, 10 miles southeast of Edmonds and 546 feet lower, has a last frost 1 day earlier (March 8), a first frost 6 days later (November 23), a season 9 days longer.

The first measurable snow (0.1 inch or more) in Edmonds usually arrives around December 26, and the last of the season around February 8. Those are the middle dates across the winters of 1991–2020 at Seattle Sand Pt Wsfo, WA, 9.7 miles away: half of years saw snow earlier, half later. Snow fell in 62% of those winters. The last 32°F night of spring typically comes 29 days after the last snow.

ZIP 98020 is 8 miles from Everett Snohomish Airport, WA, which stands at 606 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 12 other ZIP codes share the station; its figures are presented in full for 98012 (Mill Creek). The 2023 USDA Plant Hardiness Zone Map lists ZIP 98020 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.