Frost dates for Portland WFO, OR
At Portland WFO, the median last spring frost (32°F) is Mar 13 and the median first fall frost is Nov 22, for a typical growing season of 251 days. For a 90% chance that the last frost has passed, wait until Apr 5. Nearby ZIP codes are in USDA hardiness zones 8b to 9a.
- Mar 13Last spring frost (median)50% chance of 32°F after this date
- Apr 5Safer planting date10% chance of 32°F after this date
- Nov 22First fall frost (median)50% chance of 32°F by this date
- 251 daysGrowing season (median)between 32°F freezes
Last spring frost dates
The chance that the temperature drops to the threshold after each date.
| Temperature | 90% chance later | 50% chance later | 10% chance later |
|---|---|---|---|
| 36°F | Mar 22 | Apr 10 | May 1 |
| 32°F | Feb 20 | Mar 13 | Apr 5 |
| 28°F | Dec 27 | Feb 12 | Mar 7 |
| 24°F | Dec 6 | Jan 10 | Feb 20 |
First fall frost dates
The chance that the temperature has dropped to the threshold by each date.
| Temperature | 10% chance by | 50% chance by | 90% chance by |
|---|---|---|---|
| 36°F | Oct 20 | Nov 5 | Nov 22 |
| 32°F | Nov 3 | Nov 22 | Dec 14 |
| 28°F | Nov 15 | Dec 10 | Jan 22 |
| 24°F | Nov 27 | Dec 26 | Feb 7 |
Growing season length
Days between the last spring and first fall freeze, as the length reached in 9, 5 and 1 out of 10 years.
| Temperature | 9 in 10 years at least | 5 in 10 years at least | 1 in 10 years at least |
|---|---|---|---|
| 36°F | 179 days | 206 days | 232 days |
| 32°F | 224 days | 251 days | 286 days |
| 28°F | 265 days | 307 days | 350 days |
| 24°F | 312 days | 351 days | 365 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 94% |
| 24°F | 63% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 97220 | 9a | 20 to 25°F | 2 km |
| 97230 | 9a | 20 to 25°F | 3 km |
| 98683 | 8b | 15 to 20°F | 5 km |
| 97213 | 8b | 15 to 20°F | 5 km |
| 97216 | 9a | 20 to 25°F | 5 km |
| 97233 | 9a | 20 to 25°F | 6 km |
| 97215 | 9a | 20 to 25°F | 7 km |
| 97266 | 9a | 20 to 25°F | 9 km |
| 97236 | 9a | 20 to 25°F | 9 km |
Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.
About this station
- NOAA station ID USC00356750, at 45.5606, -122.5383, elevation 6 m (21 ft).
- Data quality: Representative (10+ years), 23 years of freeze data.
- Average days per year at or below 32°F: 28.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Portland Intl Airport (6 km)
- Portland Troutdale Airport (10 km)
- Troutdale (12 km)
- Portland Kgw-Tv (13 km)
- Oregon City (23 km)
- Nature Park-Beaverton (24 km)
- Beaverton 2 SSW (25 km)
- Portland-Hillsboro Airport (32 km)
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual/seasonal normals by station (version 1.0.1), file dated June 27, 2023; documentation.
- USDA Agricultural Research Service and PRISM Group, Oregon State University, 2023 Plant Hardiness Zone Map ZIP code tables (CONUS, Alaska, Hawaii, Puerto Rico), files dated November 17, 2023. Data © PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 1, 2026. Official map: planthardiness.ars.usda.gov.
- U.S. Census Bureau, 2024 Gazetteer ZIP Code Tabulation Areas file, dated August 30, 2024 (ZIP centroids used to find the nearest station).
Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.