Frost dates for Armour, SD
At Armour, the median last spring frost (32°F) is May 3 and the median first fall frost is Oct 6, for a typical growing season of 157 days. For a 90% chance that the last frost has passed, wait until May 18. Nearby ZIP codes are in USDA hardiness zone 5a.
- May 3Last spring frost (median)50% chance of 32°F after this date
- May 18Safer planting date10% chance of 32°F after this date
- Oct 6First fall frost (median)50% chance of 32°F by this date
- 157 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 30 | May 12 | May 26 |
| 32°F | Apr 17 | May 3 | May 18 |
| 28°F | Apr 6 | Apr 21 | May 7 |
| 24°F | Mar 28 | Apr 11 | Apr 26 |
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 16 | Sep 28 | Oct 10 |
| 32°F | Sep 23 | Oct 6 | Oct 21 |
| 28°F | Oct 1 | Oct 16 | Oct 30 |
| 24°F | Oct 10 | Oct 27 | Nov 8 |
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 | 121 days | 139 days | 156 days |
| 32°F | 138 days | 157 days | 176 days |
| 28°F | 156 days | 176 days | 197 days |
| 24°F | 175 days | 198 days | 218 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 |
|---|---|---|---|
| 57313 | 5a | -20 to -15°F | 1 km |
| 57328 | 5a | -20 to -15°F | 16 km |
| 57330 | 5a | -20 to -15°F | 16 km |
| 57364 | 5a | -20 to -15°F | 26 km |
| 57344 | 5a | -20 to -15°F | 27 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 USC00390296, at 43.3131, -98.3486, elevation 460 m (1,510 ft).
- Data quality: Representative (10+ years), 16 years of freeze data.
- Average days per year at or below 32°F: 156.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Wagner (26 km)
- Pickstown (31 km)
- Pickstown 4ssw (37 km)
- White Lake (49 km)
- Tyndall (53 km)
- Mitchell 2 N (54 km)
- Mitchell (55 km)
- Bonesteel (55 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.