Frost Dates for 97203 — Portland, Oregon

Half of springs at Vancouver Pearson Airport, WA see their last 32°F night by March 29; only one in ten is past it by March 6, and one in ten still has one after April 18. Planting tender crops after April 5 leaves a 30% risk of a frost on them, after April 12 20%, and after April 18 10%. The 20 days between the even-odds date and the one-in-ten date is narrower than at 64% of the 103 Oregon stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 9 in half of years, as early as October 22 one year in ten, and holds off past November 30 one year in ten. A hard freeze of 28°F follows 17 days later, around November 26; in spring the one-in-ten date for 28°F is March 27, 22 days before the 32°F one. The freeze-free season lasts 223 days in a typical year, longer than at 68% of the 103 Oregon stations; it reaches 252 days one year in ten and falls short of 196 one year in ten. On average 45 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 26 days longer, to about April 24, and return around October 24. Nights of 24°F, cold enough to damage hardier plants, come in 94% of winters and 16°F in 22%.

August is the warmest month at Vancouver Pearson Airport, WA, averaging 82°F by day and 57°F at night; January is the coldest at 47°F and 34°F. A freezing night is all but certain in every month from December to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 42% of years.

Warmth for growing adds up to 2,573 growing degree days a year (base 50°F), more than at 73% of the 103 Oregon stations. 30% of them (781) have built up by the end of June, and August adds the most, 601. Precipitation totals 37.4 inches a year, most in December (6.1") and least in July (0.4"); May to September bring 17% of it.

The nearest other station, Portland Kgw-Tv, OR, 5 miles southeast of Portland, has a last frost 32 days earlier (February 25), a first frost 22 days later (December 1), a season 57 days longer.

Measurable snow is rare here: only 11 of 27 winters from 1991 to 2020 recorded 0.1 inch or more at Vancouver 4 NNE, WA, 7.4 miles away, so there is no typical first-snow date to plan around.

ZIP 97203 is 5 miles from Vancouver Pearson Airport, WA, which stands at 30 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station; its figures are presented in full for 98661 (Vancouver). The 2023 USDA Plant Hardiness Zone Map lists ZIP 97203 in zone 9a, the band where the coldest night of the year averaged 20 to 25°F (-6.7 to -3.9°C) over 1991–2020; a zone describes winter lows, not frost dates.