Frost dates for Headworks Portland Wtr B, OR
At Headworks Portland Wtr B, the median last spring frost (32°F) is Mar 27 and the median first fall frost is Nov 18, for a typical growing season of 239 days. For a 90% chance that the last frost has passed, wait until Apr 20. Nearby ZIP codes are in USDA hardiness zones 8a to 8b.
- Mar 27Last spring frost (median)50% chance of 32°F after this date
- Apr 20Safer planting date10% chance of 32°F after this date
- Nov 18First fall frost (median)50% chance of 32°F by this date
- 239 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 | Apr 7 | Apr 26 | May 12 |
| 32°F | Feb 26 | Mar 27 | Apr 20 |
| 28°F | Jan 2 | Feb 14 | Mar 12 |
| 24°F | Dec 9 | Jan 16 | Feb 21 |
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 12 | Oct 29 | Nov 18 |
| 32°F | Oct 26 | Nov 18 | Dec 10 |
| 28°F | Nov 12 | Dec 9 | Jan 19 |
| 24°F | Nov 29 | Dec 29 | Feb 9 |
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 | 160 days | 186 days | 212 days |
| 32°F | 205 days | 239 days | 274 days |
| 28°F | 261 days | 303 days | 344 days |
| 24°F | 310 days | 350 days | 365 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 97% |
| 24°F | 65% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 97019 | 8b | 15 to 20°F | 5 km |
| 97055 | 8b | 15 to 20°F | 10 km |
| 97011 | 8a | 10 to 15°F | 11 km |
| 97009 | 8b | 15 to 20°F | 14 km |
| 97067 | 8a | 10 to 15°F | 19 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 USC00353770, at 45.4486, -122.1547, elevation 228 m (748 ft).
- Data quality: Standard (24+ years of data), 29 years of freeze data.
- Average days per year at or below 32°F: 32.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Troutdale (22 km)
- Portland Troutdale Airport (23 km)
- Estacada 2 SE (24 km)
- Bonneville Dam (26 km)
- Portland WFO (32 km)
- Cascade Locks (34 km)
- Government Camp (36 km)
- Oregon City (37 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.