Frost Dates for 98826 — Leavenworth, Washington

Half of springs at Plain, WA see their last 32°F night by May 22; only one in ten is past it by May 2, and one in ten still has one after June 13. Planting tender crops after May 31 leaves a 30% risk of a frost on them, after June 5 20%, and after June 13 10%. The 22 days between the even-odds date and the one-in-ten date is wider than at 71% 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 September 22 in half of years, as early as September 7 one year in ten, and holds off past October 4 one year in ten. A hard freeze of 28°F follows 12 days later, around October 4; in spring the one-in-ten date for 28°F is May 20, 24 days before the 32°F one. The freeze-free season lasts 121 days in a typical year, shorter than at 96% of the 113 Washington stations; it reaches 144 days one year in ten and falls short of 97 one year in ten. On average 177 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 22 days longer, to about June 13, and return around September 8. Severe cold of 16°F or below comes every winter, usually between November 24 and March 1.

July is the warmest month at Plain, WA, averaging 82°F by day and 50°F at night; December is the coldest at 32°F and 21°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From July to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 89% of years and June still brings one in 28% of years.

Warmth for growing adds up to 1,691 growing degree days a year (base 50°F), fewer than at 81% of the 113 Washington stations. 25% of them (429) have built up by the end of June, and July adds the most, 498. Precipitation totals 27.4 inches a year, most in December (5.0") and least in August (0.4"); May to September bring 14% of it.

The nearest other station, Leavenworth 3 S, WA, 12 miles south of Leavenworth and 808 feet lower, has a last frost 12 days earlier (May 10), a first frost 8 days later (September 30), a season 21 days longer.

The first measurable snow (0.1 inch or more) in Leavenworth usually arrives around November 8, and the last of the season around March 29. Those are the middle dates across the winters of 1991–2020 at Plain, WA, 5.8 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 54 days after the last snow.

ZIP 98826 is 6 miles from Plain, WA, which stands at 1,936 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 98826 in zone 7a, the band where the coldest night of the year averaged 0 to 5°F (-17.8 to -15.0°C) over 1991–2020; a zone describes winter lows, not frost dates.