Frost dates by ZIP code: The nearest NOAA stations to your ZIP, 1991-2020 normals
Enter a five-digit ZIP code. PlainClimate finds its center (Census Bureau 2024) and the five nearest NOAA stations with frost dates, and shows each station's last spring and first autumn 32°F dates with its distance and elevation.
Frost dates near ZIP 97233
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 97233 in zone 9a (the coldest night of a typical year: 20 to 25°F).
The nearest station, Portland Weather Office, OR, is 4 miles from the ZIP's center: its last spring frost comes after March 13 in half of years and after April 5 in one year in ten.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Portland Weather Office, OR | 4 mi | 21 ft | March 13 | April 5 | November 22 | – |
| Portland Troutdale Airport, OR | 5 mi | 29 ft | March 16 | April 12 | November 20 | 9a |
| Troutdale, OR | 6 mi | 33 ft | March 26 | April 21 | November 17 | 9a |
| Portland, ORPortland International Airport | 7 mi | 19 ft | March 13 | April 1 | November 19 | 9a |
| Portland Kgw-Tv, OR | 9 mi | 159 ft | February 25 | March 21 | December 1 | 9a |
Frost comes later in spring at higher and colder stations and earlier in low, open ground: prefer a station at a similar elevation to yours. Hardiness zone in the table: the USDA's rule (the average of each year's coldest night, 1991-2020) applied to the station's own record.
Every frost threshold at Portland Weather Office
NOAA publishes the dates for several temperatures and odds. A 30% spring date means a 3-in-10 chance of a later frost (the convention almanacs use); 50% is the median; 10% the cautious date.
| Threshold | Spring, 10% | Spring, 30% | Spring, 50% | Spring, 90% | Autumn, 50% | Autumn, 10% |
|---|---|---|---|---|---|---|
| 36°F (light frost) | May 1 | April 19 | April 10 | March 22 | November 5 | October 20 |
| 32°F | April 5 | March 24 | March 13 | February 20 | November 22 | November 3 |
| 28°F (hard freeze) | March 7 | February 24 | February 12 | December 27 | December 10 | November 15 |
| 24°F | February 20 | February 1 | January 10 | December 6 | December 26 | November 27 |
Source: NOAA NCEI 1991-2020 annual normals; ZIP centers: Census Bureau 2024 Gazetteer; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. Autumn 10%: one year in ten has its first frost before this date.