Last spring frost
May 23
Frost Dates for Custer, SD
First fall frost
Sep 24
Growing season
122 days
Hardiness zone
5a
In an average year around Custer, SD, the last spring frost (32°F) is about May 23 and the first fall frost is about Sep 24, giving roughly a 122-day growing season. To be safe most years, wait until May 10 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Jun 19 | Jun 4 | May 22 |
| Freeze (32°F) | Jun 6 | May 23 | May 10 |
| Hard (28°F) | May 24 | May 10 | Apr 29 |
| Severe (24°F) | May 12 | Apr 29 | Apr 14 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 19 | Jun 15 | Jun 12 | Jun 7 | Jun 4 | Jun 1 | May 30 | May 27 | May 22 |
| 32°F | Jun 6 | Jun 1 | May 30 | May 27 | May 23 | May 20 | May 18 | May 15 | May 10 |
| 28°F | May 24 | May 18 | May 15 | May 13 | May 10 | May 8 | May 5 | May 2 | Apr 29 |
| 24°F | May 12 | May 8 | May 4 | May 2 | Apr 29 | Apr 26 | Apr 22 | Apr 19 | Apr 14 |
| 20°F | May 2 | Apr 27 | Apr 23 | Apr 20 | Apr 17 | Apr 14 | Apr 11 | Apr 6 | Mar 31 |
| 16°F | Apr 23 | Apr 17 | Apr 13 | Apr 9 | Apr 5 | Apr 2 | Mar 29 | Mar 24 | Mar 17 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Aug 29 | Sep 11 | Sep 26 |
| Freeze (32°F) | Sep 9 | Sep 24 | Oct 9 |
| Hard (28°F) | Sep 23 | Oct 5 | Oct 20 |
| Severe (24°F) | Oct 1 | Oct 16 | Oct 31 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 29 | Sep 2 | Sep 6 | Sep 9 | Sep 11 | Sep 15 | Sep 18 | Sep 21 | Sep 26 |
| 32°F | Sep 9 | Sep 15 | Sep 19 | Sep 22 | Sep 24 | Sep 28 | Oct 1 | Oct 4 | Oct 9 |
| 28°F | Sep 23 | Sep 28 | Oct 1 | Oct 3 | Oct 5 | Oct 9 | Oct 12 | Oct 15 | Oct 20 |
| 24°F | Oct 1 | Oct 5 | Oct 8 | Oct 12 | Oct 16 | Oct 19 | Oct 22 | Oct 26 | Oct 31 |
| 20°F | Oct 7 | Oct 13 | Oct 17 | Oct 21 | Oct 24 | Oct 27 | Oct 31 | Nov 3 | Nov 8 |
| 16°F | Oct 14 | Oct 19 | Oct 24 | Oct 28 | Nov 1 | Nov 4 | Nov 8 | Nov 13 | Nov 19 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: Custer Co Ap, Sd, about 1.9 miles away@if(!empty($station['elevation_ft'])), at 5,545 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in Custer, SD?
On average, the last spring frost (32°F) around Custer, SD is about May 23. In cooler years it can run later, so for a safer bet many gardeners wait until May 10.
When is the first frost in the fall?
The first fall frost around Custer, SD typically arrives about Sep 24. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around May 23 on average, or May 10 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 122 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 57730 Planting calendar → South Dakota frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026