Frost dates for Portland, Oregon
Oregon · first & last freeze, from NOAA 1991–2020 climate normals
In a typical year, the last spring freeze around Portland comes near February 25 and the first fall freeze near December 1. One year in ten, a freeze still arrives after March 21 in spring — and one year in ten, the first fall freeze has already landed by November 10. NCEI's own growing-season statistic (days between freezes, percentiled per year) puts the median at 280 days.
Freeze-date probabilities, three thresholds
| Threshold | Last spring — 9 in 10 years past by | Last spring — typical (median) | Last spring — 1 in 10 years later than | First fall — 1 in 10 years by | First fall — typical (median) | First fall — 9 in 10 years by |
|---|---|---|---|---|---|---|
| 36°F — near-freezing (frost can occur) | March 7 | March 29 | April 21 | October 28 | November 12 | December 1 |
| 32°F — freezing | January 24 | February 25 | March 21 | November 10 | December 1 | December 27 |
| 28°F — hard freeze | December 21 | January 31 | February 26 | November 25 | December 20 | January 30 |
Measured at Portland Kgw-Tv, OR (USC00356749), 2.3 mi from the city's census reference point, elev. 159 ft. NOAA/NCEI 1991–2020 normals. Read each date column as odds over the 30-year record — e.g. "9 in 10 years past by" means only one spring in ten saw a later freeze than that date.
Frost-free windows (computed)
| Window (32°F ends) | Opens | Closes | Length |
|---|---|---|---|
| Cautious (1-in-10 freeze risk at each end) | March 21 | November 10 | 234 days |
| Typical (median freeze dates) | February 25 | December 1 | 279 days |
| Gambler's (9-in-10 freeze risk at each end) | January 24 | December 27 | 337 days |
Pure arithmetic on the freeze-date percentiles above — the "cautious" window opens on the date only 1 year in 10 still sees a later spring freeze, and closes on the date by which only 1 year in 10 has already frozen.
About this city's numbers
- Census entity: Portland city, Oregon — official 2024 population estimate 635,749.
- Weather station: Portland Kgw-Tv, OR (USC00356749), 2.3 mi from the city's census-gazetteer reference point at elevation 159 ft. Frost dates are that station's history — neighborhoods vary.
- Data pulled 2026-09-05; normals period 1991-2020 (replaced by NOAA roughly once a decade).
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