Frost Dates for 98843 — Orondo, Washington

Half of springs at Waterville, WA see their last 32°F night by May 14; only one in ten is past it by April 28, and one in ten still has one after June 4. Planting tender crops after May 22 leaves a 30% risk of a frost on them, after May 29 20%, and after June 4 10%. The 21 days between the even-odds date and the one-in-ten date is wider than at 65% of the 113 Washington stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.

In fall the first 32°F night comes by October 1 in half of years, as early as September 18 one year in ten, and holds off past October 14 one year in ten. A hard freeze of 28°F follows 11 days later, around October 12; in spring the one-in-ten date for 28°F is May 15, 20 days before the 32°F one. The freeze-free season lasts 140 days in a typical year, shorter than at 90% of the 113 Washington stations; it reaches 161 days one year in ten and falls short of 112 one year in ten. On average 161 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 23 days longer, to about June 6, and return around September 19. Severe cold of 16°F or below comes every winter, usually between November 11 and March 6.

July is the warmest month at Waterville, WA, averaging 84°F by day and 53°F at night; December is the coldest at 31°F and 16°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 81% of years and June still brings one in 15% of years.

Warmth for growing adds up to 1,949 growing degree days a year (base 50°F), fewer than at 51% of the 113 Washington stations. 26% of them (502) have built up by the end of June, and July adds the most, 563. Precipitation totals 11.6 inches a year, most in December (2.0") and least in August (0.3"); May to September bring 28% of it.

The nearest other station, Chelan, WA, 7 miles northeast of Orondo and 1,470 feet lower, has a last frost 27 days earlier (April 17), a first frost 21 days later (October 22), a season 47 days longer.

The first measurable snow (0.1 inch or more) in Orondo usually arrives around November 24, and the last of the season around March 17. Those are the middle dates across the winters of 1991–2020 at Waterville, WA, 6.7 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 58 days after the last snow.

ZIP 98843 is 7 miles from Waterville, WA, which stands at 2,664 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 98843 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.