Frost dates for Swan Falls Ph, ID
At Swan Falls Ph, the median last spring frost (32°F) is Apr 12 and the median first fall frost is Oct 26, for a typical growing season of 193 days. For a 90% chance that the last frost has passed, wait until May 6. Nearby ZIP codes are in USDA hardiness zone 7a.
- Apr 12Last spring frost (median)50% chance of 32°F after this date
- May 6Safer planting date10% chance of 32°F after this date
- Oct 26First fall frost (median)50% chance of 32°F by this date
- 193 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 11 | Apr 28 | May 21 |
| 32°F | Mar 23 | Apr 12 | May 6 |
| 28°F | Feb 28 | Mar 23 | Apr 25 |
| 24°F | Feb 7 | Feb 28 | Apr 2 |
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 30 | Oct 15 | Oct 29 |
| 32°F | Oct 9 | Oct 26 | Nov 9 |
| 28°F | Oct 21 | Nov 5 | Nov 21 |
| 24°F | Oct 28 | Nov 15 | Dec 2 |
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 | 136 days | 166 days | 189 days |
| 32°F | 162 days | 193 days | 219 days |
| 28°F | 187 days | 224 days | 254 days |
| 24°F | 217 days | 257 days | 287 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
Closest ZIP codes (each is closer to another station)
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 83634 | 7a | 0 to 5°F | 23 km |
| 83641 | 7a | 0 to 5°F | 24 km |
| 83686 | 7a | 0 to 5°F | 34 km |
| 83709 | 7a | 0 to 5°F | 35 km |
| 83642 | 7a | 0 to 5°F | 37 km |
| 83705 | 7a | 0 to 5°F | 37 km |
| 83624 | 7a | 0 to 5°F | 40 km |
| 83706 | 7a | 0 to 5°F | 41 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 USC00108928, at 43.2436, -116.3783, elevation 709 m (2,325 ft).
- Data quality: Standard (24+ years of data), 27 years of freeze data.
- Average days per year at or below 32°F: 97.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Grand View 4 NW (30 km)
- Reynolds (30 km)
- Murphy 10 W (30 km)
- Boise Air Terminal (38 km)
- Boise Lucky Peak Dam (41 km)
- Nampa Sugar Factory (43 km)
- Silver City 5 W (46 km)
- Deer Flat Dam (48 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.