Frost dates for 57312Alpena, SD
The average last spring frost in Alpena is May 9 and the average first fall frost is September 28, giving a typical growing season of about 140 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 9
- Average first fall frost
- Sep 28
- Growing season
- 140 days
Safer after May 24 (1-in-10 risk)
Possible by Sep 14 (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 6 · May 19 · Jun 2 | Sep 6 · Sep 19 · Oct 1 | 122 days | 100% |
| Frost / freeze (32°F) | Apr 27 · May 9 · May 24 | Sep 14 · Sep 28 · Oct 10 | 140 days | 100% |
| Hard freeze (28°F) | Apr 15 · Apr 30 · May 13 | Sep 23 · Oct 6 · Oct 19 | 158 days | 100% |
Planting calendar for Alpena
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 8 – Jun 14 |
| Tomatoes | Transplant outdoors | May 25 – Jun 8 |
| Peppers | Start seeds indoors | Apr 8 – May 9 |
| Peppers | Transplant outdoors | Jun 8 – Jul 9 |
| Eggplant | Start seeds indoors | Apr 25 – May 24 |
| Eggplant | Transplant outdoors | Jun 8 – Jul 9 |
| Cucumbers | Sow outdoors | Jun 8 – Jun 18 |
| Summer squash | Sow outdoors | May 25 – Jul 9 |
| Winter squash & pumpkins | Sow outdoors | Jun 8 – Jul 9 |
| Snap beans | Sow outdoors | May 25 – Jul 11 |
| Sweet corn | Sow outdoors | May 25 – Jun 8 |
| Watermelon & cantaloupe | Sow outdoors | Jun 8 – Jul 9 |
| Okra | Sow outdoors | Jun 1 – Jun 24 |
| Peas | Sow outdoors (spring) | Apr 8 – May 24 |
| Potatoes | Plant outdoors (spring) | Apr 8 – Jun 8 |
| Onions | Start seeds indoors (spring) | Feb 25 – Mar 24 |
| Onions | Transplant outdoors (spring) | Apr 25 – May 24 |
| Broccoli | Start seeds indoors (spring) | Mar 21 – Apr 24 |
| Broccoli | Transplant outdoors (spring) | Apr 25 – May 24 |
| Broccoli | Start seeds indoors (fall) | May 29 – Jun 8 |
| Broccoli | Transplant outdoors (fall) | Jun 28 – Jul 9 |
| Cabbage | Start seeds indoors (spring) | Mar 11 – Apr 8 |
| Cabbage | Transplant outdoors (spring) | Apr 8 – May 9 |
| Cabbage | Start seeds indoors (fall) | May 19 – Jun 18 |
| Cabbage | Transplant outdoors (fall) | Jun 18 – Jul 19 |
| Leaf lettuce | Sow outdoors (spring) | Apr 8 – Jun 24 |
| Leaf lettuce | Sow outdoors (fall) | Jun 18 – Aug 4 |
| Spinach | Sow outdoors (spring) | Apr 1 – May 15 |
| Spinach | Sow outdoors (fall) | Jul 5 – Aug 9 |
| Radishes | Sow outdoors (spring) | Apr 8 – May 29 |
| Radishes | Sow outdoors (fall) | Jun 18 – Aug 19 |
| Kale | Sow outdoors (spring) | Apr 25 – May 15 |
| Kale | Sow outdoors (fall) | Jun 11 – Jul 19 |
| Carrots | Sow outdoors (spring) | May 9 – Jun 24 |
| Carrots | Sow outdoors (fall) | May 19 – Jul 4 |
| Garlic | Plant outdoors (fall) | Sep 18 – Oct 19 |
Where these dates come from
ZIP code 57312 is matched to the NOAA station Forestburg 4 Nne, SD, 27.5 km away, at 1,277 ft elevation (68 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Forestburg 4 Nne, SD (used) | 1,277 ft | May 9 | Sep 28 |
| Wessington Springs, SD | 1,715 ft | May 2 | Oct 8 |
| Huron Rgnl Ap, SD | 1,280 ft | May 6 | Oct 2 |
| Gann Valley 3 Nne, SD | 1,646 ft | May 7 | Oct 1 |
Frost dates near Alpena
- Lane, SD 57358 · last May 2, first Oct 8
- Virgil, SD 57379 · last May 6, first Oct 2
- Woonsocket, SD 57385 · last May 9, first Sep 28
- Wessington Springs, SD 57382 · last May 2, first Oct 8
- Huron, SD 57350 · last May 6, first Oct 2
- Wolsey, SD 57384 · last May 6, first Oct 2
- Artesian, SD 57314 · last May 9, first Sep 28
- Letcher, SD 57359 · last Apr 30, first Oct 5
Frequently asked questions
- When is the last frost in Alpena, SD?
- For ZIP code 57312, the average last spring frost (32°F) is May 9, based on NOAA 1991-2020 climate normals for the Forestburg 4 Nne, SD weather station. There is a 1-in-10 chance of a frost after May 24.
- When is the first frost in Alpena, SD?
- The average first fall frost (32°F) is September 28. There is a 1-in-10 chance of frost by September 14, so tender plants are at risk from that point on.
- How long is the growing season in 57312?
- 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.