Frost dates for Custer Co Airport, SD
At Custer Co Airport, the median last spring frost (32°F) is May 23 and the median first fall frost is Sep 24, for a typical growing season of 122 days. For a 90% chance that the last frost has passed, wait until Jun 6. Nearby ZIP codes are in USDA hardiness zone 5a.
- May 23Last spring frost (median)50% chance of 32°F after this date
- Jun 6Safer planting date10% chance of 32°F after this date
- Sep 24First fall frost (median)50% chance of 32°F by this date
- 122 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 22 | Jun 4 | Jun 19 |
| 32°F | May 10 | May 23 | Jun 6 |
| 28°F | Apr 29 | May 10 | May 24 |
| 24°F | Apr 14 | Apr 29 | May 12 |
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 11 | Sep 26 |
| 32°F | Sep 9 | Sep 24 | Oct 9 |
| 28°F | Sep 23 | Oct 5 | Oct 20 |
| 24°F | Oct 1 | Oct 16 | Oct 31 |
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 | 77 days | 98 days | 118 days |
| 32°F | 101 days | 122 days | 143 days |
| 28°F | 127 days | 147 days | 167 days |
| 24°F | 149 days | 168 days | 188 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 |
|---|---|---|---|
| 57730 | 5a | -20 to -15°F | 3 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 USW00094032, at 43.7331, -103.6114, elevation 1690 m (5,545 ft).
- Data quality: Representative (10+ years), 21 years of freeze data.
- Average days per year at or below 32°F: 195.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Custer (5 km)
- Mount Rushmore Nmem (20 km)
- Wind Cave (22 km)
- Hill City (23 km)
- Edgemont 23 NNW (27 km)
- Hot Springs (35 km)
- Pactola Dam (38 km)
- Johnson Siding (42 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.