Frost dates for Diablo Dam, WA
At Diablo Dam, the median last spring frost (32°F) is Apr 10 and the median first fall frost is Nov 1, for a typical growing season of 203 days. For a 90% chance that the last frost has passed, wait until May 1. Nearby ZIP codes are in USDA hardiness zones 6a to 8b.
- Apr 10Last spring frost (median)50% chance of 32°F after this date
- May 1Safer planting date10% chance of 32°F after this date
- Nov 1First fall frost (median)50% chance of 32°F by this date
- 203 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 16 | May 2 | May 17 |
| 32°F | Mar 22 | Apr 10 | May 1 |
| 28°F | Feb 23 | Mar 13 | Apr 4 |
| 24°F | Jan 13 | Feb 20 | Mar 13 |
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 7 | Oct 19 | Nov 1 |
| 32°F | Oct 19 | Nov 1 | Nov 20 |
| 28°F | Nov 1 | Nov 20 | Dec 11 |
| 24°F | Nov 16 | Dec 6 | Jan 12 |
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 | 151 days | 170 days | 190 days |
| 32°F | 180 days | 203 days | 230 days |
| 28°F | 219 days | 247 days | 278 days |
| 24°F | 258 days | 292 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% |
Closest ZIP codes (each is closer to another station)
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 98283 | 7a | 0 to 5°F | 15 km |
| 98267 | 7a | 0 to 5°F | 37 km |
| 98237 | 8a | 10 to 15°F | 46 km |
| 98833 | 6a | -10 to -5°F | 47 km |
| 98852 | 6b | -5 to 0°F | 52 km |
| 98244 | 8a | 10 to 15°F | 57 km |
| 98241 | 8a | 10 to 15°F | 57 km |
| 98255 | 8b | 15 to 20°F | 66 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 USC00452157, at 48.7142, -121.1431, elevation 272 m (891 ft).
- Data quality: Standard (24+ years of data), 29 years of freeze data.
- Average days per year at or below 32°F: 86.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Ross Dam (5 km)
- Newhalem (8 km)
- Darrington 21 NNE (29 km)
- Upper Baker Dam (41 km)
- Concrete Ppl Fish Station (48 km)
- Stehekin 4 NW (51 km)
- Mazama (54 km)
- Darrington Ranger Station (61 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.