Frost Dates for 97754 — Prineville, Oregon

Half of springs at Prineville, OR see their last 32°F night by June 1; only one in ten is past it by May 8, and one in ten still has one after June 22. Planting tender crops after June 10 leaves a 30% risk of a frost on them, after June 15 20%, and after June 22 10%. The 21 days between the even-odds date and the one-in-ten date is narrower than at 55% of the 103 Oregon 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 September 22 in half of years, as early as August 31 one year in ten, and holds off past October 9 one year in ten. A hard freeze of 28°F follows 16 days later, around October 8; in spring the one-in-ten date for 28°F is June 1, 21 days before the 32°F one. The freeze-free season lasts 113 days in a typical year, shorter than at 90% of the 103 Oregon stations; it reaches 142 days one year in ten and falls short of 83 one year in ten. On average 166 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 18 days longer, to about June 19, and return around September 4. Severe cold of 16°F or below comes every winter, usually between November 23 and February 26.

July is the warmest month at Prineville, OR, averaging 87°F by day and 49°F at night; December is the coldest at 42°F and 24°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). July is the only month with under a 10% chance of a 32°F night. In spring, June still brings one in 49% of years.

Warmth for growing adds up to 2,063 growing degree days a year (base 50°F), fewer than at 60% of the 103 Oregon stations. 27% of them (554) have built up by the end of June, and July adds the most, 558. Precipitation totals 10.5 inches a year, most in May (1.4") and least in September (0.3"); May to September bring 32% of it.

The nearest other station, Redmond Roberts Field, OR, 19 miles west of Prineville and 167 feet higher, has a last frost 8 days later (June 9), a first frost 8 days earlier (September 14), a season 15 days shorter.

The first measurable snow (0.1 inch or more) in Prineville usually arrives around November 30, and the last of the season around March 15. Those are the middle dates across the winters of 1991–2020 at Prineville, OR, 6 miles away: half of years saw snow earlier, half later. Snow fell in 92% of those winters. The last 32°F night of spring typically comes 78 days after the last snow.

ZIP 97754 is 6 miles from Prineville, OR, which stands at 2,876 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 97754 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.