Frost dates for Portland
The typical last spring frost in Portland is Mar 13, and the typical first fall frost is Nov 19. These dates come from Portland International Airport, and the growing season between them is 247 days.
NCEI U.S. Climate Normals 1991-2020, annual/seasonal (c20230404), USW00024229
This season's measured frost
No freeze has been recorded yet this fall at Portland International Airport; the lowest reading since July 1 is 39F on Oct 12, against a typical first frost date of Nov 19.
In 2026, the last spring freeze at Portland International Airport was on Mar 26 with a low of 32F, 13 days later than the typical date of Mar 13.
Readings come from official daily lows in the daily climate report of the National Weather Service, via the Iowa Environmental Mesonet.
Early, typical and late years for Portland
| Year type | Last spring frost | First fall frost |
|---|---|---|
| Early year (1 in 10) | Feb 22 | Oct 29 |
| Typical year | Mar 13 | Nov 19 |
| Late year (1 in 10) | Apr 1 | Dec 10 |
For spring, an early year means 1 year in 10 has a last freeze before the early date, and a late year means 1 year in 10 has a last freeze after the late date. For fall, an early year means 1 year in 10 has a first freeze by the early date, and a late year means it holds off past the late date.
The growing season in a typical year is 247 days, with the shortest at 219 days and the longest at 277 days in 1 year in 10.
Frost and freeze thresholds
| Last spring frost | First fall frost | |
|---|---|---|
| Light frost (36F) | Apr 6 | Nov 2 |
| Freeze (32F) | Mar 13 | Nov 19 |
| Hard freeze (28F) | Feb 16 | Dec 5 |
Clear, calm nights can see frost on plants at a low of 36F. A low of 32F is a freeze, and most tender plants are killed at 28F, a hard freeze.
More weather for Portland
A typical date is the median: half of years have an earlier last spring frost, half a later one. An early year means 1 year in 10, and a late year means 1 year in 10. Dates come from the U.S. Climate Normals for 1991-2020, published by NOAA's National Centers for Environmental Information, using a daily low of 32F or below as a freeze.
The daily climate report is issued by the local National Weather Service forecast office and delivered to this page by the Iowa Environmental Mesonet of Iowa State University. Under 17 U.S.C. 105, no copyright attaches to the government-produced figures on this page, including reports, alerts, station observations, and normals, which were created by the National Weather Service and other NOAA offices. The notice that 17 U.S.C. 403 requires appears in this sentence. It does not imply endorsement by or affiliation with those agencies. See: Data sources and attribution.