Frost Dates for 99344 — Othello, Washington

Half of springs at Connell 1 W, WA see their last 32°F night by April 30; only one in ten is past it by April 12, and one in ten still has one after May 15. Planting tender crops after May 6 leaves a 30% risk of a frost on them, after May 10 20%, and after May 15 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 81% of the 113 Washington stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 12 in half of years, as early as September 29 one year in ten, and holds off past October 26 one year in ten. A hard freeze of 28°F follows 12 days later, around October 24; in spring the one-in-ten date for 28°F is May 1, 14 days before the 32°F one. The freeze-free season lasts 165 days in a typical year, shorter than at 75% of the 113 Washington stations; it reaches 187 days one year in ten and falls short of 144 one year in ten. On average 115 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 13, and return around October 1. Severe cold of 16°F or below comes in 96% of winters, usually between December 6 and February 3.

July is the warmest month at Connell 1 W, WA, averaging 90°F by day and 55°F at night; December is the coldest at 39°F and 27°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 48% of years.

Warmth for growing adds up to 2,714 growing degree days a year (base 50°F), more than at 82% of the 113 Washington stations. 31% of them (849) have built up by the end of June, and July adds the most, 694. Precipitation totals 8.8 inches a year, most in December (1.3") and least in August (0.2"); May to September bring 25% of it.

The nearest other station, Smyrna, WA, 23 miles west of Othello and 460 feet lower, has a last frost 7 days earlier (April 23), the same first-frost date, a season 7 days longer.

The first measurable snow (0.1 inch or more) in Othello usually arrives around December 1, and the last of the season around February 26. Those are the middle dates across the winters of 1991–2020 at Hatton 9 SE, WA, 26.1 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 63 days after the last snow.

ZIP 99344 is 19 miles from Connell 1 W, WA, which stands at 1,020 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 99344 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.