Frost dates for 57473Seneca, SD
The average last spring frost in Seneca is May 14 and the average first fall frost is September 29, giving a typical growing season of about 138 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 14
- Average first fall frost
- Sep 29
- Growing season
- 138 days
Safer after May 25 (1-in-10 risk)
Possible by Sep 16 (1-in-10 risk)
Last frost typically in 192 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 11 · May 23 · Jun 4 | Sep 8 · Sep 21 · Oct 3 | 122 days | 100% |
| Frost / freeze (32°F) | Apr 30 · May 14 · May 25 | Sep 16 · Sep 29 · Oct 12 | 138 days | 100% |
| Hard freeze (28°F) | Apr 20 · May 4 · May 17 | Sep 24 · Oct 7 · Oct 21 | 156 days | 100% |
Planting calendar for Seneca
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 13 – Jun 19 |
| Tomatoes | Transplant outdoors | May 30 – Jun 9 |
| Peppers | Start seeds indoors | Apr 13 – May 14 |
| Peppers | Transplant outdoors | Jun 13 – Jul 14 |
| Eggplant | Start seeds indoors | Apr 30 – May 29 |
| Eggplant | Transplant outdoors | Jun 13 – Jul 14 |
| Cucumbers | Sow outdoors | Jun 13 – Jun 19 |
| Summer squash | Sow outdoors | May 30 – Jul 14 |
| Winter squash & pumpkins | Sow outdoors | Jun 13 – Jul 14 |
| Snap beans | Sow outdoors | May 30 – Jul 12 |
| Sweet corn | Sow outdoors | May 30 – Jun 9 |
| Watermelon & cantaloupe | Sow outdoors | Jun 13 – Jul 14 |
| Okra | Sow outdoors | Jun 6 – Jun 29 |
| Peas | Sow outdoors (spring) | Apr 13 – May 29 |
| Potatoes | Plant outdoors (spring) | Apr 13 – Jun 13 |
| Onions | Start seeds indoors (spring) | Mar 2 – Mar 29 |
| Onions | Transplant outdoors (spring) | Apr 30 – May 29 |
| Broccoli | Start seeds indoors (spring) | Mar 26 – Apr 29 |
| Broccoli | Transplant outdoors (spring) | Apr 30 – May 29 |
| Broccoli | Start seeds indoors (fall) | May 30 – Jun 9 |
| Broccoli | Transplant outdoors (fall) | Jun 29 – Jul 10 |
| Cabbage | Start seeds indoors (spring) | Mar 16 – Apr 13 |
| Cabbage | Transplant outdoors (spring) | Apr 13 – May 14 |
| Cabbage | Start seeds indoors (fall) | May 20 – Jun 19 |
| Cabbage | Transplant outdoors (fall) | Jun 19 – Jul 20 |
| Leaf lettuce | Sow outdoors (spring) | Apr 13 – Jun 29 |
| Leaf lettuce | Sow outdoors (fall) | Jun 19 – Aug 5 |
| Spinach | Sow outdoors (spring) | Apr 6 – May 20 |
| Spinach | Sow outdoors (fall) | Jul 6 – Aug 10 |
| Radishes | Sow outdoors (spring) | Apr 13 – Jun 3 |
| Radishes | Sow outdoors (fall) | Jun 19 – Aug 20 |
| Kale | Sow outdoors (spring) | Apr 30 – May 20 |
| Kale | Sow outdoors (fall) | Jun 12 – Jul 20 |
| Carrots | Sow outdoors (spring) | May 14 – Jun 29 |
| Carrots | Sow outdoors (fall) | May 20 – Jul 5 |
| Garlic | Plant outdoors (fall) | Sep 19 – Oct 20 |
Where these dates come from
ZIP code 57473 is matched to the NOAA station Highmore 23 N, SD, 20.3 km away, at 1,870 ft elevation (3 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Highmore 23 N, SD (used) | 1,870 ft | May 14 | Sep 29 |
| Faulkton 1 Nw, SD | 1,597 ft | May 10 | Sep 28 |
| Gettysburg, SD | 2,084 ft | May 7 | Oct 2 |
| Roscoe, SD | 1,835 ft | May 7 | Oct 3 |
Frost dates near Seneca
- Onaka, SD 57466 · last May 7, first Oct 3
- Tolstoy, SD 57475 · last May 7, first Oct 2
- Lebanon, SD 57455 · last May 7, first Oct 2
- Faulkton, SD 57438 · last May 10, first Sep 28
- Hoven, SD 57450 · last May 7, first Oct 2
- Orient, SD 57467 · last May 10, first Sep 28
- Gettysburg, SD 57442 · last May 7, first Oct 2
- Cresbard, SD 57435 · last May 10, first Sep 28
Frequently asked questions
- When is the last frost in Seneca, SD?
- For ZIP code 57473, the average last spring frost (32°F) is May 14, based on NOAA 1991-2020 climate normals for the Highmore 23 N, SD weather station. There is a 1-in-10 chance of a frost after May 25.
- When is the first frost in Seneca, 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 57473?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 138 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.