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 97331
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 97331 in zone 8b (the coldest night of a typical year: 15 to 20°F).
The nearest station, Corvallis, OR, is 7 miles from the ZIP's center: its last spring frost comes after April 17 in half of years and after May 8 in one year in ten. By the USDA's method its plant hardiness zone is 8b.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Corvallis, ORCorvallis State University | 7 mi | 225 ft | April 17 | May 8 | October 28 | 8b |
| Corvallis Water Bureau, OR | 9 mi | 592 ft | May 15 | June 2 | October 8 | 8b |
| Corvallis (10 mi SSW), OR | 10 mi | 312 ft | April 11 | May 5 | October 30 | – |
| Lebanon, OR | 19 mi | 330 ft | March 14 | April 14 | November 18 | – |
| Falls City, OR2 mi SSW | 21 mi | 690 ft | April 18 | May 6 | November 7 | 8b |
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 Corvallis
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) | June 2 | May 20 | May 11 | April 25 | October 10 | September 23 |
| 32°F | May 8 | April 27 | April 17 | March 22 | October 28 | October 5 |
| 28°F (hard freeze) | April 5 | March 16 | March 1 | January 25 | November 17 | October 22 |
| 24°F | February 24 | February 11 | January 24 | December 10 | December 5 | November 7 |
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.