Frost Dates for 97370 — Philomath, Oregon

Half of springs at Corvallis Water Bureau, OR see their last 32°F night by May 15; only one in ten is past it by April 28, and one in ten still has one after June 2. Planting tender crops after May 23 leaves a 30% risk of a frost on them, after May 29 20%, and after June 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 8 in half of years, as early as September 24 one year in ten, and holds off past October 26 one year in ten. A hard freeze of 28°F follows 20 days later, around October 28; in spring the one-in-ten date for 28°F is May 10, 23 days before the 32°F one. The freeze-free season lasts 145 days in a typical year, shorter than at 81% of the 103 Oregon stations; it reaches 172 days one year in ten and falls short of 119 one year in ten. On average 83 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 24 days longer, to about June 8, and return around September 19. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 64%.

August is the warmest month at Corvallis Water Bureau, OR, averaging 83°F by day and 46°F at night; December is the coldest at 46°F and 28°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 82% of years and June still brings one in 13% of years.

Warmth for growing adds up to 1,709 growing degree days a year (base 50°F), fewer than at 80% of the 103 Oregon stations. 26% of them (442) have built up by the end of June, and August adds the most, 445. Precipitation totals 68.8 inches a year, most in December (13.4") and least in July (0.3"); May to September bring 10% of it.

The nearest other station, Corvallis 10 SSW, OR, 12 miles southeast of Philomath and 280 feet lower, has a last frost 34 days earlier (April 11), a first frost 22 days later (October 30), a season 58 days longer.

The first measurable snow (0.1 inch or more) in Philomath usually arrives around December 19, and the last of the season around February 28. Those are the middle dates across the winters of 1991–2020 at Corvallis Water Bureau, OR, 5 miles away: half of years saw snow earlier, half later. Snow fell in 73% of those winters. The last 32°F night of spring typically comes 76 days after the last snow.

ZIP 97370 is 5 miles from Corvallis Water Bureau, OR, which stands at 592 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 97370 in zone 8b, the band where the coldest night of the year averaged 15 to 20°F (-9.4 to -6.7°C) over 1991–2020; a zone describes winter lows, not frost dates.