Frost dates for 57346Stephan, SD
The average last spring frost in Stephan is May 10 and the average first fall frost is September 29, giving a typical growing season of about 140 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 10
- Average first fall frost
- Sep 29
- Growing season
- 140 days
Safer after May 24 (1-in-10 risk)
Possible by Sep 16 (1-in-10 risk)
Last frost typically in 188 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | May 9 · May 21 · Jun 2 | Sep 8 · Sep 21 · Oct 3 | 123 days | 100% |
| Frost / freeze (32°F) | Apr 29 · May 10 · May 24 | Sep 16 · Sep 29 · Oct 11 | 140 days | 100% |
| Hard freeze (28°F) | Apr 17 · May 2 · May 14 | Sep 23 · Oct 6 · Oct 19 | 158 days | 100% |
Planting calendar for Stephan
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Apr 9 – Jun 15 |
| Tomatoes | Transplant outdoors | May 26 – Jun 9 |
| Peppers | Start seeds indoors | Apr 9 – May 10 |
| Peppers | Transplant outdoors | Jun 9 – Jul 10 |
| Eggplant | Start seeds indoors | Apr 26 – May 25 |
| Eggplant | Transplant outdoors | Jun 9 – Jul 10 |
| Cucumbers | Sow outdoors | Jun 9 – Jun 19 |
| Summer squash | Sow outdoors | May 26 – Jul 10 |
| Winter squash & pumpkins | Sow outdoors | Jun 9 – Jul 10 |
| Snap beans | Sow outdoors | May 26 – Jul 12 |
| Sweet corn | Sow outdoors | May 26 – Jun 9 |
| Watermelon & cantaloupe | Sow outdoors | Jun 9 – Jul 10 |
| Okra | Sow outdoors | Jun 2 – Jun 25 |
| Peas | Sow outdoors (spring) | Apr 9 – May 25 |
| Potatoes | Plant outdoors (spring) | Apr 9 – Jun 9 |
| Onions | Start seeds indoors (spring) | Feb 26 – Mar 25 |
| Onions | Transplant outdoors (spring) | Apr 26 – May 25 |
| Broccoli | Start seeds indoors (spring) | Mar 22 – Apr 25 |
| Broccoli | Transplant outdoors (spring) | Apr 26 – May 25 |
| Broccoli | Start seeds indoors (fall) | May 30 – Jun 9 |
| Broccoli | Transplant outdoors (fall) | Jun 29 – Jul 10 |
| Cabbage | Start seeds indoors (spring) | Mar 12 – Apr 9 |
| Cabbage | Transplant outdoors (spring) | Apr 9 – May 10 |
| Cabbage | Start seeds indoors (fall) | May 20 – Jun 19 |
| Cabbage | Transplant outdoors (fall) | Jun 19 – Jul 20 |
| Leaf lettuce | Sow outdoors (spring) | Apr 9 – Jun 25 |
| Leaf lettuce | Sow outdoors (fall) | Jun 19 – Aug 5 |
| Spinach | Sow outdoors (spring) | Apr 2 – May 16 |
| Spinach | Sow outdoors (fall) | Jul 6 – Aug 10 |
| Radishes | Sow outdoors (spring) | Apr 9 – May 30 |
| Radishes | Sow outdoors (fall) | Jun 19 – Aug 20 |
| Kale | Sow outdoors (spring) | Apr 26 – May 16 |
| Kale | Sow outdoors (fall) | Jun 12 – Jul 20 |
| Carrots | Sow outdoors (spring) | May 10 – Jun 25 |
| Carrots | Sow outdoors (fall) | May 20 – Jul 5 |
| Garlic | Plant outdoors (fall) | Sep 19 – Oct 20 |
Where these dates come from
ZIP code 57346 is matched to the NOAA station Stephan 2 Nw, SD, 2.2 km away, at 1,805 ft elevation (19 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Stephan 2 Nw, SD (used) | 1,805 ft | May 10 | Sep 29 |
| Lake Sharpe Prj, SD | 1,461 ft | May 6 | Oct 5 |
| Highmore 1 W, SD | 1,888 ft | May 12 | Oct 1 |
| Harrold 12 Ssw, SD | 1,701 ft | May 17 | Sep 24 |
Frost dates near Stephan
- Lower Brule, SD 57548 · last May 6, first Oct 5
- Fort Thompson, SD 57339 · last May 6, first Oct 5
- Highmore, SD 57345 · last May 12, first Oct 1
- Holabird, SD 57540 · last May 12, first Oct 1
- Gann Valley, SD 57341 · last May 6, first Oct 1
- Harrold, SD 57536 · last May 17, first Sep 24
- Ree Heights, SD 57371 · last May 3, first Oct 3
- Reliance, SD 57569 · last May 12, first Sep 28
Frequently asked questions
- When is the last frost in Stephan, SD?
- For ZIP code 57346, the average last spring frost (32°F) is May 10, based on NOAA 1991-2020 climate normals for the Stephan 2 Nw, SD weather station. There is a 1-in-10 chance of a frost after May 24.
- When is the first frost in Stephan, SD?
- The average first fall frost (32°F) is September 29. There is a 1-in-10 chance of frost by September 16, so tender plants are at risk from that point on.
- How long is the growing season in 57346?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 140 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.