Frost dates for Riddle, OR
At Riddle, the median last spring frost (32°F) is Mar 31 and the median first fall frost is Nov 6, for a typical growing season of 221 days. For a 90% chance that the last frost has passed, wait until Apr 27. Nearby ZIP codes are in USDA hardiness zones 8b to 9a.
- Mar 31Last spring frost (median)50% chance of 32°F after this date
- Apr 27Safer planting date10% chance of 32°F after this date
- Nov 6First fall frost (median)50% chance of 32°F by this date
- 221 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 8 | Apr 27 | May 14 |
| 32°F | Feb 27 | Mar 31 | Apr 27 |
| 28°F | Dec 22 | Feb 20 | Mar 31 |
| 24°F | Nov 19 | Jan 6 | Feb 24 |
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 28 | Oct 14 | Nov 7 |
| 32°F | Oct 11 | Nov 6 | Dec 13 |
| 28°F | Oct 28 | Dec 10 | Feb 12 |
| 24°F | Nov 3 | Dec 21 | Feb 17 |
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 | 145 days | 172 days | 204 days |
| 32°F | 184 days | 221 days | 266 days |
| 28°F | 234 days | 292 days | 353 days |
| 24°F | 304 days | 364 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 | 48% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 97469 | 8b | 15 to 20°F | 6 km |
| 97417 | 8b | 15 to 20°F | 12 km |
| 97496 | 9a | 20 to 25°F | 16 km |
| 97457 | 8b | 15 to 20°F | 16 km |
| 97442 | 8b | 15 to 20°F | 20 km |
| 97429 | 8b | 15 to 20°F | 25 km |
| 97410 | 8b | 15 to 20°F | 26 km |
| 97416 | 9a | 20 to 25°F | 29 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 USC00357169, at 42.9508, -123.3572, elevation 207 m (680 ft).
- Data quality: Standard (24+ years of data), 26 years of freeze data.
- Average days per year at or below 32°F: 33.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Roseburg Kqen (29 km)
- Roseburg Regional Airport (32 km)
- Winchester (37 km)
- Sexton Summit (39 km)
- Idleyld Park 4 NE (56 km)
- Powers (58 km)
- Grants Pass (59 km)
- Lost Creek Dam (64 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.