Frost dates for Forest Grove, OR
At Forest Grove, the median last spring frost (32°F) is Apr 16 and the median first fall frost is Oct 26, for a typical growing season of 192 days. For a 90% chance that the last frost has passed, wait until May 5. Nearby ZIP codes are in USDA hardiness zone 8b.
- Apr 16Last spring frost (median)50% chance of 32°F after this date
- May 5Safer planting date10% chance of 32°F after this date
- Oct 26First fall frost (median)50% chance of 32°F by this date
- 192 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 19 | May 4 | May 25 |
| 32°F | Mar 26 | Apr 16 | May 5 |
| 28°F | Feb 21 | Mar 19 | Apr 12 |
| 24°F | Jan 5 | Feb 17 | Mar 16 |
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 | Sep 24 | Oct 8 | Oct 30 |
| 32°F | Oct 6 | Oct 26 | Nov 14 |
| 28°F | Oct 23 | Nov 11 | Dec 5 |
| 24°F | Nov 6 | Nov 30 | Jan 1 |
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 | 131 days | 155 days | 183 days |
| 32°F | 165 days | 192 days | 222 days |
| 28°F | 201 days | 236 days | 272 days |
| 24°F | 248 days | 287 days | 331 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 99% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 97113 | 8b | 15 to 20°F | 5 km |
| 97116 | 8b | 15 to 20°F | 8 km |
| 97119 | 8b | 15 to 20°F | 11 km |
| 97106 | 8b | 15 to 20°F | 15 km |
| 97125 | 8b | 15 to 20°F | 18 km |
| 97117 | 8b | 15 to 20°F | 22 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 USC00352997, at 45.5247, -123.1025, elevation 55 m (180 ft).
- Data quality: Standard (24+ years of data), 28 years of freeze data.
- Average days per year at or below 32°F: 61.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Portland-Hillsboro Airport (12 km)
- Nature Park-Beaverton (21 km)
- Beaverton 2 SSW (23 km)
- Rex 1 S (29 km)
- Portland Kgw-Tv (32 km)
- Scappoose Ind Airport (33 km)
- Mc Minnville (34 km)
- McMinnville Muni Airport (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.