Frost dates for 57787Union Center, SD
The average last spring frost in Union Center is May 16 and the average first fall frost is September 26, giving a typical growing season of about 131 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 16
- Average first fall frost
- Sep 26
- Growing season
- 131 days
Safer after May 27 (1-in-10 risk)
Possible by Sep 11 (1-in-10 risk)
Last frost typically in 194 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 14 · May 25 · Jun 6 | Sep 1 · Sep 17 · Sep 28 | 114 days | 100% |
| Frost / freeze (32°F) | May 4 · May 16 · May 27 | Sep 11 · Sep 26 · Oct 8 | 131 days | 100% |
| Hard freeze (28°F) | Apr 23 · May 6 · May 21 | Sep 18 · Oct 3 · Oct 18 | 149 days | 100% |
Planting calendar for Union Center
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 15 – Jun 21 |
| Tomatoes | Transplant outdoors | Jun 1 – Jun 6 |
| Peppers | Start seeds indoors | Apr 15 – May 16 |
| Peppers | Transplant outdoors | Jun 15 – Jul 16 |
| Eggplant | Start seeds indoors | May 2 – May 31 |
| Eggplant | Transplant outdoors | Jun 15 – Jul 16 |
| Cucumbers | Sow outdoors | Jun 15 – Jun 16 |
| Summer squash | Sow outdoors | Jun 1 – Jul 16 |
| Winter squash & pumpkins | Sow outdoors | Jun 15 – Jul 16 |
| Snap beans | Sow outdoors | Jun 1 – Jul 9 |
| Sweet corn | Sow outdoors | Jun 1 – Jun 6 |
| Watermelon & cantaloupe | Sow outdoors | Jun 15 – Jul 16 |
| Okra | Sow outdoors | Jun 8 – Jul 1 |
| Peas | Sow outdoors (spring) | Apr 15 – May 31 |
| Potatoes | Plant outdoors (spring) | Apr 15 – Jun 15 |
| Onions | Start seeds indoors (spring) | Mar 4 – Mar 31 |
| Onions | Transplant outdoors (spring) | May 2 – May 31 |
| Broccoli | Start seeds indoors (spring) | Mar 28 – May 1 |
| Broccoli | Transplant outdoors (spring) | May 2 – May 31 |
| Broccoli | Start seeds indoors (fall) | May 27 – Jun 6 |
| Broccoli | Transplant outdoors (fall) | Jun 26 – Jul 7 |
| Cabbage | Start seeds indoors (spring) | Mar 18 – Apr 15 |
| Cabbage | Transplant outdoors (spring) | Apr 15 – May 16 |
| Cabbage | Start seeds indoors (fall) | May 17 – Jun 16 |
| Cabbage | Transplant outdoors (fall) | Jun 16 – Jul 17 |
| Leaf lettuce | Sow outdoors (spring) | Apr 15 – Jul 1 |
| Leaf lettuce | Sow outdoors (fall) | Jun 16 – Aug 2 |
| Spinach | Sow outdoors (spring) | Apr 8 – May 22 |
| Spinach | Sow outdoors (fall) | Jul 3 – Aug 7 |
| Radishes | Sow outdoors (spring) | Apr 15 – Jun 5 |
| Radishes | Sow outdoors (fall) | Jun 16 – Aug 17 |
| Kale | Sow outdoors (spring) | May 2 – May 22 |
| Kale | Sow outdoors (fall) | Jun 9 – Jul 17 |
| Carrots | Sow outdoors (spring) | May 16 – Jul 1 |
| Carrots | Sow outdoors (fall) | May 17 – Jul 2 |
| Garlic | Plant outdoors (fall) | Sep 16 – Oct 17 |
Where these dates come from
ZIP code 57787 is matched to the NOAA station Red Owl, SD, 13.9 km away, at 2,773 ft elevation (314 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Red Owl, SD (used) | 2,773 ft | May 16 | Sep 26 |
| Maurine 12Sw, SD | 2,629 ft | May 13 | Sep 28 |
| Elm Springs 3 Ese, SD | 2,645 ft | May 8 | Oct 3 |
| Plainview 6 Ssw, SD | 2,377 ft | May 15 | Sep 27 |
Frost dates near Union Center
- Enning, SD 57737 · last May 16, first Sep 26
- White Owl, SD 57792 · last May 16, first Sep 26
- Mud Butte, SD 57758 · last May 11, first Sep 28
- Vale, SD 57788 · last May 8, first Oct 1
- Wasta, SD 57791 · last May 10, first Oct 1
- Newell, SD 57760 · last May 8, first Oct 1
- Howes, SD 57748 · last May 15, first Sep 27
- Sturgis, SD 57785 · last May 8, first Oct 3
Frequently asked questions
- When is the last frost in Union Center, SD?
- For ZIP code 57787, the average last spring frost (32°F) is May 16, based on NOAA 1991-2020 climate normals for the Red Owl, SD weather station. There is a 1-in-10 chance of a frost after May 27.
- When is the first frost in Union Center, SD?
- The average first fall frost (32°F) is September 26. There is a 1-in-10 chance of frost by September 11, so tender plants are at risk from that point on.
- How long is the growing season in 57787?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 131 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.