Frost dates for Massacre Rocks State Park, ID
At Massacre Rocks State Park, the median last spring frost (32°F) is May 20 and the median first fall frost is Sep 26, for a typical growing season of 125 days. For a 90% chance that the last frost has passed, wait until Jun 9. Nearby ZIP codes are in USDA hardiness zone 6a.
- May 20Last spring frost (median)50% chance of 32°F after this date
- Jun 9Safer planting date10% chance of 32°F after this date
- Sep 26First fall frost (median)50% chance of 32°F by this date
- 125 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 | May 21 | Jun 8 | Jun 24 |
| 32°F | May 4 | May 20 | Jun 9 |
| 28°F | Apr 16 | May 4 | May 19 |
| 24°F | Mar 27 | Apr 15 | May 4 |
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 | Aug 29 | Sep 13 | Sep 30 |
| 32°F | Sep 8 | Sep 26 | Oct 11 |
| 28°F | Sep 21 | Oct 9 | Oct 25 |
| 24°F | Oct 7 | Oct 24 | Nov 6 |
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 | 74 days | 95 days | 117 days |
| 32°F | 101 days | 125 days | 149 days |
| 28°F | 132 days | 157 days | 181 days |
| 24°F | 165 days | 191 days | 217 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 83211 | 6a | -10 to -5°F | 7 km |
| 83271 | 6a | -10 to -5°F | 26 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 USC00105678, at 42.6681, -112.9981, elevation 1279 m (4,195 ft).
- Data quality: Representative (10+ years), 17 years of freeze data.
- Average days per year at or below 32°F: 160.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- American Falls (22 km)
- American Falls 6 NE (23 km)
- Aberdeen Exp. Station (35 km)
- Minidoka Dam (41 km)
- Pocatello Regional Airport (45 km)
- Malta 4 ESE (49 km)
- Malta (50 km)
- Pocatello City (51 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.