Frost Dates for 98019 — Duvall, Washington

Half of springs at Monroe, WA see their last 32°F night by April 17; only one in ten is past it by March 29, and one in ten still has one after May 7. Planting tender crops after April 27 leaves a 30% risk of a frost on them, after May 1 20%, and after May 7 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 October 23 in half of years, as early as October 7 one year in ten, and holds off past November 9 one year in ten. A hard freeze of 28°F follows 16 days later, around November 8; in spring the one-in-ten date for 28°F is April 14, 23 days before the 32°F one. The freeze-free season lasts 188 days in a typical year, shorter than at 51% of the 113 Washington stations; it reaches 212 days one year in ten and falls short of 163 one year in ten. On average 60 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 18 days longer, to about May 5, and return around October 6. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 54%.

August is the warmest month at Monroe, WA, averaging 75°F by day and 52°F at night; December is the coldest at 43°F and 32°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 83% of years and May still brings one in 21% of years.

Warmth for growing adds up to 1,550 growing degree days a year (base 50°F), fewer than at 86% of the 113 Washington stations. 28% of them (431) have built up by the end of June, and August adds the most, 406. Precipitation totals 50.8 inches a year, most in November (7.2") and least in July (1.2"); May to September bring 22% of it.

The nearest other station, Seattle Sand Pt Wsfo, WA, 14 miles west of Duvall, has a last frost 40 days earlier (March 8), a first frost 31 days later (November 23), a season 71 days longer.

The first measurable snow (0.1 inch or more) in Duvall usually arrives around November 26, and the last of the season around April 2. Those are the middle dates across the winters of 1991–2020 at Tolt S Fk Rsvr, WA, 12.9 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 15 days after the last snow.

ZIP 98019 is 8 miles from Monroe, WA, which stands at 120 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station; its figures are presented in full for 98290 (Snohomish). The 2023 USDA Plant Hardiness Zone Map lists ZIP 98019 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.