Frost Dates for 98356 — Morton, Washington

Half of springs at Glenoma, WA see their last 32°F night by April 24; only one in ten is past it by March 31, and one in ten still has one after May 12. Planting tender crops after May 1 leaves a 30% risk of a frost on them, after May 5 20%, and after May 12 10%. The 18 days between the even-odds date and the one-in-ten date is narrower than at 56% of the 113 Washington stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 15 in half of years, as early as September 24 one year in ten, and holds off past November 8 one year in ten. A hard freeze of 28°F follows 21 days later, around November 5; in spring the one-in-ten date for 28°F is April 18, 24 days before the 32°F one. The freeze-free season lasts 176 days in a typical year, shorter than at 63% of the 113 Washington stations; it reaches 205 days one year in ten and falls short of 145 one year in ten. On average 82 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 19 days longer, to about May 13, and return around September 25. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 51%.

July is the warmest month at Glenoma, WA, averaging 79°F by day and 50°F at night; December is the coldest at 44°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 August the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 86% of years and May still brings one in 31% of years.

Warmth for growing adds up to 1,713 growing degree days a year (base 50°F), fewer than at 78% of the 113 Washington stations. 30% of them (509) have built up by the end of June, and July adds the most, 446.

The nearest other station, Mayfield Pwr Plt, WA, 15 miles west of Morton and 560 feet lower, has a last frost 17 days earlier (April 7), a first frost 29 days later (November 13), a season 39 days longer.

Measurable snow is rare here: only 12 of 28 winters from 1991 to 2020 recorded 0.1 inch or more at Mayfield Pwr Plt, WA, 14.8 miles away, so there is no typical first-snow date to plan around.

ZIP 98356 is 8 miles from Glenoma, WA, which stands at 840 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 98356 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.