Frost Dates for 98823 — Ephrata, Washington

Half of springs at Ephrata Municipal Airport, WA see their last 32°F night by April 22; only one in ten is past it by April 8, and one in ten still has one after May 6. Planting tender crops after April 29 leaves a 30% risk of a frost on them, after May 1 20%, and after May 6 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 17 in half of years, as early as October 3 one year in ten, and holds off past October 28 one year in ten. A hard freeze of 28°F follows 10 days later, around October 27; in spring the one-in-ten date for 28°F is April 25, 11 days before the 32°F one. The freeze-free season lasts 175 days in a typical year, shorter than at 65% of the 113 Washington stations; it reaches 196 days one year in ten and falls short of 156 one year in ten. On average 121 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 12 days longer, to about May 4, and return around October 5. Severe cold of 16°F or below comes every winter, usually between November 27 and February 12.

July is the warmest month at Ephrata Municipal Airport, WA, averaging 89°F by day and 61°F at night; January 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 September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 23% of years.

Warmth for growing adds up to 3,010 growing degree days a year (base 50°F), more than at 88% of the 113 Washington stations. 31% of them (946) have built up by the end of June, and July adds the most, 784. Precipitation totals 7.7 inches a year, most in December (1.1") and least in August (0.2"); May to September bring 29% of it.

The nearest other station, Moses Lake Grant Co Airport, WA, 13 miles southeast of Ephrata, has a last frost 5 days later (April 27), a first frost 9 days earlier (October 8), a season 10 days shorter.

The first measurable snow (0.1 inch or more) in Ephrata usually arrives around December 9, and the last of the season around February 3. Those are the middle dates across the winters of 1991–2020 at Quincy, WA, 14.1 miles away: half of years saw snow earlier, half later. Snow fell in 71% of those winters. The last 32°F night of spring typically comes 78 days after the last snow.

ZIP 98823 is 3 miles from Ephrata Municipal Airport, WA, which stands at 1,252 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 98823 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.