Frost dates for 57481Westport, SD
The average last spring frost in Westport is May 7 and the average first fall frost is September 29, giving a typical growing season of about 145 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 7
- Average first fall frost
- Sep 29
- Growing season
- 145 days
Safer after May 22 (1-in-10 risk)
Possible by Sep 18 (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 4 · May 18 · May 30 | Sep 10 · Sep 22 · Oct 3 | 126 days | 100% |
| Frost / freeze (32°F) | Apr 26 · May 7 · May 22 | Sep 18 · Sep 29 · Oct 12 | 145 days | 100% |
| Hard freeze (28°F) | Apr 14 · Apr 28 · May 12 | Sep 25 · Oct 7 · Oct 22 | 162 days | 100% |
Planting calendar for Westport
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 6 – Jun 12 |
| Tomatoes | Transplant outdoors | May 23 – Jun 9 |
| Peppers | Start seeds indoors | Apr 6 – May 7 |
| Peppers | Transplant outdoors | Jun 6 – Jul 7 |
| Eggplant | Start seeds indoors | Apr 23 – May 22 |
| Eggplant | Transplant outdoors | Jun 6 – Jul 7 |
| Cucumbers | Sow outdoors | Jun 6 – Jun 19 |
| Summer squash | Sow outdoors | May 23 – Jul 7 |
| Winter squash & pumpkins | Sow outdoors | Jun 6 – Jul 7 |
| Snap beans | Sow outdoors | May 23 – Jul 12 |
| Sweet corn | Sow outdoors | May 23 – Jun 9 |
| Watermelon & cantaloupe | Sow outdoors | Jun 6 – Jul 7 |
| Okra | Sow outdoors | May 30 – Jun 22 |
| Peas | Sow outdoors (spring) | Apr 6 – May 22 |
| Potatoes | Plant outdoors (spring) | Apr 6 – Jun 6 |
| Onions | Start seeds indoors (spring) | Feb 23 – Mar 22 |
| Onions | Transplant outdoors (spring) | Apr 23 – May 22 |
| Broccoli | Start seeds indoors (spring) | Mar 19 – Apr 22 |
| Broccoli | Transplant outdoors (spring) | Apr 23 – May 22 |
| Broccoli | Start seeds indoors (fall) | May 30 – Jun 9 |
| Broccoli | Transplant outdoors (fall) | Jun 29 – Jul 10 |
| Cabbage | Start seeds indoors (spring) | Mar 9 – Apr 6 |
| Cabbage | Transplant outdoors (spring) | Apr 6 – May 7 |
| Cabbage | Start seeds indoors (fall) | May 20 – Jun 19 |
| Cabbage | Transplant outdoors (fall) | Jun 19 – Jul 20 |
| Leaf lettuce | Sow outdoors (spring) | Apr 6 – Jun 22 |
| Leaf lettuce | Sow outdoors (fall) | Jun 19 – Aug 5 |
| Spinach | Sow outdoors (spring) | Mar 30 – May 13 |
| Spinach | Sow outdoors (fall) | Jul 6 – Aug 10 |
| Radishes | Sow outdoors (spring) | Apr 6 – May 27 |
| Radishes | Sow outdoors (fall) | Jun 19 – Aug 20 |
| Kale | Sow outdoors (spring) | Apr 23 – May 13 |
| Kale | Sow outdoors (fall) | Jun 12 – Jul 20 |
| Carrots | Sow outdoors (spring) | May 7 – Jun 22 |
| Carrots | Sow outdoors (fall) | May 20 – Jul 5 |
| Garlic | Plant outdoors (fall) | Sep 19 – Oct 20 |
Where these dates come from
ZIP code 57481 is matched to the NOAA station Columbia 8 N, SD, 22.3 km away, at 1,305 ft elevation (96 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Columbia 8 N, SD (used) | 1,305 ft | May 7 | Sep 29 |
| Aberdeen, SD | 1,302 ft | May 9 | Sep 26 |
| Aberdeen 3 E, SD | 1,301 ft | May 8 | Sep 29 |
| Leola, SD | 1,580 ft | May 9 | Sep 28 |
Frost dates near Westport
- Barnard, SD 57426 · last May 7, first Sep 29
- Aberdeen, SD 57402 · last May 7, first Sep 29
- Frederick, SD 57441 · last May 4, first Oct 2
- Columbia, SD 57433 · last May 7, first Sep 29
- Leola, SD 57456 · last May 9, first Sep 28
- Bath, SD 57427 · last May 9, first Sep 26
- Warner, SD 57479 · last May 9, first Sep 26
- Hecla, SD 57446 · last May 7, first Sep 29
Frequently asked questions
- When is the last frost in Westport, SD?
- For ZIP code 57481, the average last spring frost (32°F) is May 7, based on NOAA 1991-2020 climate normals for the Columbia 8 N, SD weather station. There is a 1-in-10 chance of a frost after May 22.
- When is the first frost in Westport, SD?
- The average first fall frost (32°F) is September 29. There is a 1-in-10 chance of frost by September 18, so tender plants are at risk from that point on.
- How long is the growing season in 57481?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 145 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.