Frost Dates for 98926 — Ellensburg, Washington

Half of springs at Ellensburg Bowers Field, WA see their last 32°F night by April 28; only one in ten is past it by April 13, and one in ten still has one after May 12. Planting tender crops after May 3 leaves a 30% risk of a frost on them, after May 7 20%, and after May 12 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 88% of the 113 Washington stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 7 in half of years, as early as September 26 one year in ten, and holds off past October 22 one year in ten. A hard freeze of 28°F follows 13 days later, around October 20; in spring the one-in-ten date for 28°F is April 30, 12 days before the 32°F one. The freeze-free season lasts 163 days in a typical year, shorter than at 77% of the 113 Washington stations; it reaches 185 days one year in ten and falls short of 143 one year in ten. On average 139 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 13 days longer, to about May 11, and return around September 26. Severe cold of 16°F or below comes in 99% of winters, usually between November 29 and February 13.

July is the warmest month at Ellensburg Bowers Field, WA, averaging 86°F by day and 57°F at night; December is the coldest at 36°F and 24°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 40% of years.

Warmth for growing adds up to 2,532 growing degree days a year (base 50°F), more than at 77% of the 113 Washington stations. 30% of them (754) have built up by the end of June, and July adds the most, 669. Precipitation totals 9.2 inches a year, most in December (1.5") and least in July (0.2"); May to September bring 25% of it.

The nearest other station, Cle Elum, WA, 22 miles northwest of Ellensburg, has a last frost 15 days later (May 13), a first frost 12 days earlier (September 25), a season 31 days shorter.

The first measurable snow (0.1 inch or more) in Ellensburg usually arrives around November 25, and the last of the season around February 25. Those are the middle dates across the winters of 1991–2020 at Ellensburg, WA, 2.9 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 62 days after the last snow.

ZIP 98926 is 2 miles from Ellensburg Bowers Field, WA, which stands at 1,766 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 98926 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.