Frost dates for 57633Isabel, SD
The average last spring frost in Isabel is May 11 and the average first fall frost is September 30, giving a typical growing season of about 140 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 11
- Average first fall frost
- Sep 30
- Growing season
- 140 days
Safer after May 24 (1-in-10 risk)
Possible by Sep 16 (1-in-10 risk)
Last frost typically in 196 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 2 | 122 days | 100% |
| Frost / freeze (32°F) | Apr 30 · May 11 · May 24 | Sep 16 · Sep 30 · Oct 13 | 140 days | 100% |
| Hard freeze (28°F) | Apr 17 · May 2 · May 15 | Sep 23 · Oct 7 · Oct 20 | 157 days | 100% |
Planting calendar for Isabel
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 10 – Jun 16 |
| Tomatoes | Transplant outdoors | May 27 – Jun 10 |
| Peppers | Start seeds indoors | Apr 10 – May 11 |
| Peppers | Transplant outdoors | Jun 10 – Jul 11 |
| Eggplant | Start seeds indoors | Apr 27 – May 26 |
| Eggplant | Transplant outdoors | Jun 10 – Jul 11 |
| Cucumbers | Sow outdoors | Jun 10 – Jun 20 |
| Summer squash | Sow outdoors | May 27 – Jul 11 |
| Winter squash & pumpkins | Sow outdoors | Jun 10 – Jul 11 |
| Snap beans | Sow outdoors | May 27 – Jul 13 |
| Sweet corn | Sow outdoors | May 27 – Jun 10 |
| Watermelon & cantaloupe | Sow outdoors | Jun 10 – Jul 11 |
| Okra | Sow outdoors | Jun 3 – Jun 26 |
| Peas | Sow outdoors (spring) | Apr 10 – May 26 |
| Potatoes | Plant outdoors (spring) | Apr 10 – Jun 10 |
| Onions | Start seeds indoors (spring) | Feb 27 – Mar 26 |
| Onions | Transplant outdoors (spring) | Apr 27 – May 26 |
| Broccoli | Start seeds indoors (spring) | Mar 23 – Apr 26 |
| Broccoli | Transplant outdoors (spring) | Apr 27 – May 26 |
| Broccoli | Start seeds indoors (fall) | May 31 – Jun 10 |
| Broccoli | Transplant outdoors (fall) | Jun 30 – Jul 11 |
| Cabbage | Start seeds indoors (spring) | Mar 13 – Apr 10 |
| Cabbage | Transplant outdoors (spring) | Apr 10 – May 11 |
| Cabbage | Start seeds indoors (fall) | May 21 – Jun 20 |
| Cabbage | Transplant outdoors (fall) | Jun 20 – Jul 21 |
| Leaf lettuce | Sow outdoors (spring) | Apr 10 – Jun 26 |
| Leaf lettuce | Sow outdoors (fall) | Jun 20 – Aug 6 |
| Spinach | Sow outdoors (spring) | Apr 3 – May 17 |
| Spinach | Sow outdoors (fall) | Jul 7 – Aug 11 |
| Radishes | Sow outdoors (spring) | Apr 10 – May 31 |
| Radishes | Sow outdoors (fall) | Jun 20 – Aug 21 |
| Kale | Sow outdoors (spring) | Apr 27 – May 17 |
| Kale | Sow outdoors (fall) | Jun 13 – Jul 21 |
| Carrots | Sow outdoors (spring) | May 11 – Jun 26 |
| Carrots | Sow outdoors (fall) | May 21 – Jul 6 |
| Garlic | Plant outdoors (fall) | Sep 20 – Oct 21 |
Where these dates come from
ZIP code 57633 is matched to the NOAA station Glad Valley 2 W, SD, 29 km away, at 2,487 ft elevation (112 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Glad Valley 2 W, SD (used) | 2,487 ft | May 11 | Sep 30 |
| Timber Lake, SD | 2,173 ft | May 10 | Sep 30 |
| Dupree, SD | 2,388 ft | May 8 | Oct 1 |
| Mc Intosh 6 Se, SD | 2,179 ft | May 9 | Sep 30 |
Frost dates near Isabel
- Timber Lake, SD 57656 · last May 10, first Sep 30
- Glencross, SD 57630 · last May 10, first Sep 30
- Mc Intosh, SD 57641 · last May 9, first Sep 30
- Lantry, SD 57636 · last May 8, first Oct 1
- Whitehorse, SD 57661 · last May 10, first Sep 30
- Dupree, SD 57623 · last May 8, first Oct 1
- Eagle Butte, SD 57625 · last May 8, first Oct 1
- Bullhead, SD 57621 · last May 12, first Sep 28
Frequently asked questions
- When is the last frost in Isabel, SD?
- For ZIP code 57633, the average last spring frost (32°F) is May 11, based on NOAA 1991-2020 climate normals for the Glad Valley 2 W, SD weather station. There is a 1-in-10 chance of a frost after May 24.
- When is the first frost in Isabel, SD?
- The average first fall frost (32°F) is September 30. 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 57633?
- 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.