Frost Dates for 98951 — Wapato, Washington

Half of springs at Wapato, WA see their last 32°F night by April 21; only one in ten is past it by April 1, and one in ten still has one after May 7. Planting tender crops after April 28 leaves a 30% risk of a frost on them, after May 2 20%, and after May 7 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 74% 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 October 4 one year in ten, and holds off past October 27 one year in ten. A hard freeze of 28°F follows 11 days later, around October 26; in spring the one-in-ten date for 28°F is April 21, 16 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 199 days one year in ten and falls short of 156 one year in ten. On average 127 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 15 days longer, to about May 6, and return around October 5. Severe cold of 16°F or below comes in 99% of winters, usually between November 30 and February 7.

July is the warmest month at Wapato, WA, averaging 90°F by day and 59°F at night; December is the coldest at 39°F and 23°F. A freezing night is all but certain in every month from October to March (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 88% of years and May still brings one in 23% of years.

Warmth for growing adds up to 3,018 growing degree days a year (base 50°F), more than at 89% of the 113 Washington stations. 32% of them (977) have built up by the end of June, and July adds the most, 766. Precipitation totals 7.7 inches a year, most in December (1.4") and least in July (0.2"); May to September bring 25% of it.

The nearest other station, Yakima #2, WA, 10 miles northwest of Wapato and 301 feet higher, has a last frost 13 days earlier (April 8), a first frost 8 days later (October 23), a season 20 days longer.

The first measurable snow (0.1 inch or more) in Wapato usually arrives around December 6, and the last of the season around February 1. Those are the middle dates across the winters of 1991–2020 at Wapato, WA, 2.7 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 79 days after the last snow.

ZIP 98951 is 3 miles from Wapato, WA, which stands at 841 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 98948 (Toppenish). The 2023 USDA Plant Hardiness Zone Map lists ZIP 98951 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.