Frost dates for Portland Troutdale Airport, OR
At Portland Troutdale Airport, the median last spring frost (32°F) is Mar 16 and the median first fall frost is Nov 20, for a typical growing season of 250 days. For a 90% chance that the last frost has passed, wait until Apr 12. Nearby ZIP codes are in USDA hardiness zones 8b to 9a.
- Mar 16Last spring frost (median)50% chance of 32°F after this date
- Apr 12Safer planting date10% chance of 32°F after this date
- Nov 20First fall frost (median)50% chance of 32°F by this date
- 250 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 27 | Apr 19 | May 4 |
| 32°F | Feb 18 | Mar 16 | Apr 12 |
| 28°F | Dec 27 | Feb 14 | Mar 10 |
| 24°F | Dec 6 | Jan 22 | 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 11 | Oct 30 | Nov 22 |
| 32°F | Oct 30 | Nov 20 | Dec 17 |
| 28°F | Nov 15 | Dec 15 | Feb 3 |
| 24°F | Nov 30 | Jan 1 | Feb 13 |
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 | 171 days | 198 days | 226 days |
| 32°F | 216 days | 250 days | 288 days |
| 28°F | 268 days | 311 days | 358 days |
| 24°F | 317 days | 365 days | 365 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 93% |
| 24°F | 51% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 97024 | 9a | 20 to 25°F | 3 km |
| 97030 | 9a | 20 to 25°F | 5 km |
| 97080 | 8b | 15 to 20°F | 8 km |
| 97089 | 8b | 15 to 20°F | 14 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 USW00024242, at 45.5511, -122.4089, elevation 9 m (29 ft).
- Data quality: Representative (10+ years), 20 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
- Troutdale (2 km)
- Portland WFO (10 km)
- Portland Intl Airport (16 km)
- Portland Kgw-Tv (22 km)
- Headworks Portland Wtr B (23 km)
- Oregon City (27 km)
- Estacada 2 SE (32 km)
- Beaverton 2 SSW (34 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.