Frost Dates for 98856 — Twisp, Washington

Half of springs at Winthrop 1 WSW, WA see their last 32°F night by May 15; only one in ten is past it by April 30, and one in ten still has one after June 1. Planting tender crops after May 22 leaves a 30% risk of a frost on them, after May 27 20%, and after June 1 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 September 22 in half of years, as early as September 10 one year in ten, and holds off past October 2 one year in ten. A hard freeze of 28°F follows 11 days later, around October 3; in spring the one-in-ten date for 28°F is May 15, 17 days before the 32°F one. The freeze-free season lasts 127 days in a typical year, shorter than at 94% of the 113 Washington stations; it reaches 146 days one year in ten and falls short of 107 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 17 days longer, to about June 1, and return around September 9. Severe cold of 16°F or below comes every winter, usually between November 11 and March 8.

July is the warmest month at Winthrop 1 WSW, WA, averaging 86°F by day and 51°F at night; December is the coldest at 29°F and 15°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 87% of years and June still brings one in 12% of years.

Warmth for growing adds up to 1,998 growing degree days a year (base 50°F), more than at 52% of the 113 Washington stations. 28% of them (566) have built up by the end of June, and July adds the most, 567. Precipitation totals 15.3 inches a year, most in December (2.6") and least in August (0.5"); May to September bring 25% of it.

The nearest other station, Omak Airport, WA, 29 miles east of Twisp and 453 feet lower, has a last frost 15 days earlier (April 30), a first frost 15 days later (October 7), a season 33 days longer.

The first measurable snow (0.1 inch or more) in Twisp usually arrives around November 7, and the last of the season around March 17. Those are the middle dates across the winters of 1991–2020 at Winthrop 1 WSW, WA, 8.3 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 59 days after the last snow.

ZIP 98856 is 8 miles from Winthrop 1 WSW, WA, which stands at 1,749 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 98862 (Winthrop). The 2023 USDA Plant Hardiness Zone Map lists ZIP 98856 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°C) over 1991–2020; a zone describes winter lows, not frost dates.