Frost Dates for 97844 — Irrigon, Oregon

Half of springs at Boardman, OR see their last 32°F night by April 14; only one in ten is past it by March 28, and one in ten still has one after May 2. Planting tender crops after April 23 leaves a 30% risk of a frost on them, after April 27 20%, and after May 2 10%. The 18 days between the even-odds date and the one-in-ten date is narrower than at 77% of the 103 Oregon stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 21 in half of years, as early as October 5 one year in ten, and holds off past November 4 one year in ten. A hard freeze of 28°F follows 11 days later, around November 1; in spring the one-in-ten date for 28°F is April 15, 17 days before the 32°F one. The freeze-free season lasts 188 days in a typical year, shorter than at 59% of the 103 Oregon stations; it reaches 210 days one year in ten and falls short of 167 one year in ten. On average 104 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 17 days longer, to about May 1, and return around October 8. Severe cold of 16°F or below comes in 91% of winters, usually between December 13 and February 7.

July is the warmest month at Boardman, OR, averaging 91°F by day and 60°F at night; January is the coldest at 42°F and 29°F. A freezing night is all but certain in every month from November 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 83% of years and May still brings one in 13% of years.

Warmth for growing adds up to 3,212 growing degree days a year (base 50°F), more than at 98% of the 103 Oregon stations. 33% of them (1,049) have built up by the end of June, and July adds the most, 795. Precipitation totals 8.6 inches a year, most in December (1.4") and least in July (0.1"); May to September bring 23% of it.

The nearest other station, Hermiston 2 NW, OR, 10 miles east of Irrigon and 180 feet higher, has a last frost 13 days later (April 27), a first frost 14 days earlier (October 7), a season 25 days shorter.

The first measurable snow (0.1 inch or more) in Irrigon usually arrives around December 28, and the last of the season around January 25. Those are the middle dates across the winters of 1991–2020 at Boardman, OR, 8.9 miles away: half of years saw snow earlier, half later. Snow fell in 65% of those winters. The last 32°F night of spring typically comes 79 days after the last snow.

ZIP 97844 is 9 miles from Boardman, OR, which stands at 280 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 97818 (Boardman). The 2023 USDA Plant Hardiness Zone Map lists ZIP 97844 in zone 7b, the band where the coldest night of the year averaged 5 to 10°F (-15.0 to -12.2°C) over 1991–2020; a zone describes winter lows, not frost dates.