Frost dates for Stephan 2 NW, SD
At Stephan 2 NW, the median last spring frost (32°F) is May 10 and the median first fall frost is Sep 29, for a typical growing season of 140 days. For a 90% chance that the last frost has passed, wait until May 24. Nearby ZIP codes are in USDA hardiness zone 4b.
- May 10Last spring frost (median)50% chance of 32°F after this date
- May 24Safer planting date10% chance of 32°F after this date
- Sep 29First fall frost (median)50% chance of 32°F by this date
- 140 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 9 | May 21 | Jun 2 |
| 32°F | Apr 29 | May 10 | May 24 |
| 28°F | Apr 17 | May 2 | May 14 |
| 24°F | Apr 8 | Apr 22 | May 6 |
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 8 | Sep 21 | Oct 3 |
| 32°F | Sep 16 | Sep 29 | Oct 11 |
| 28°F | Sep 23 | Oct 6 | Oct 19 |
| 24°F | Sep 30 | Oct 15 | Oct 28 |
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 | 105 days | 123 days | 139 days |
| 32°F | 124 days | 140 days | 158 days |
| 28°F | 141 days | 158 days | 176 days |
| 24°F | 156 days | 175 days | 194 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 |
|---|---|---|---|
| 57346 | 4b | -25 to -20°F | 2 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 USC00397992, at 44.2661, -99.4431, elevation 550 m (1,805 ft).
- Data quality: Representative (10+ years), 17 years of freeze data.
- Average days per year at or below 32°F: 179.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Lake Sharpe Prj (22 km)
- Highmore 1 W (28 km)
- Harrold 12 SSW (31 km)
- Gann Valley 4nw (38 km)
- Gann Valley 3 NNE (43 km)
- Miller (46 km)
- Kennebec (52 km)
- Chamberlain Muni Airport (56 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.