Fall in zone 4aPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 57421 (Marshall County, SD)
Average last spring and first fall frost dates with 10%, 50% and 90% odds, from NOAA's 1991–2020 climate normals for the nearest weather station, Britton, SD (8 miles away).
- Average last spring frostMay 1350% chance of a 32°F freeze after this date
- Average first fall frostSep 2650% chance of a 32°F freeze by this date
- Growing season (frost-free)135 daysmedian, 32°F threshold
- USDA hardiness zone4a-30 to -25°F avg. coldest night
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Frost and freeze alerts from the NWS forecast for 57421, the spring soil-temperature heads-up for pre-emergent, and a short weekly yard-timing email.
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This week in your yard
As of Oct 18, 2026, from your frost dates, zone and soil temperature. Lawn timing · Vegetables · Pruning · Plants
Soil temperature now
2-inch depth
49°F Below 50°F
24-hour average · latest 50°F, as of Oct 18, 1:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Aberdeen 35 WNW (59 mi).
4-inch depth
50°F Below 50°F
24-hour average · latest 50°F, as of Oct 18, 1:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Aberdeen 35 WNW (59 mi).
Fall: Texas A&M AgriLife times fall pre-emergent (for winter weeds such as annual bluegrass) to soil cooling to about 70°F for several days. The 50–55°F band is the spring trigger. Always read and follow the product label.
7-day forecast and frost risk
The latest National Weather Service 7-day forecast and any Frost Advisory or Freeze Warning for 57421 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
Soil is 50°F at 4 inches (estimated soil temperature, not a station reading). Fall pre-emergent window is mostly past. Next: spring, when soil reaches 50°F (typically mid-April to early May).
Fertilizer window
Lawn region: North (cool-season). Timing only; always follow the product label.
- Kentucky bluegrass (cool-season): Early fall: Around Labor Day (late August–September); Late fall: Late October–November, before the ground freezes; Late spring: Optional around Memorial Day. Avoid: Early-spring and midsummer feeding (pushes top growth, favors crabgrass).
Plant now
No vegetable planting windows are open this week.
Prune now
No frost-timed pruning windows are open this week.
Spring-flowering shrubs are pruned right after their flowers fade, not by date. See the pruning guide.
Last spring frost odds
| Chance of a 32°F freeze after this date | Date |
|---|---|
| 90% (early: most years still freeze after this) | Apr 29 |
| 50% (the "average" last frost) | May 13 |
| 10% (cautious: only 1 year in 10 freezes later) | May 27 |
Most gardeners plant frost-tender crops (tomatoes, peppers, basil) after the 50% date, and closer to the 10% date for less risk.
First fall frost odds
| Chance the first 32°F freeze has happened by this date | Date |
|---|---|
| 10% (early: 1 year in 10 freezes this soon) | Sep 14 |
| 50% (the "average" first frost) | Sep 26 |
| 90% (late: most years have frozen by now) | Oct 7 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | May 23 | Sep 16 |
| 32°F (freeze) | May 13 | Sep 26 |
| 28°F (hard freeze) | May 2 | Oct 3 |
n/a means NOAA did not publish a date at that threshold for this station (usually because it rarely gets that cold).
Vegetable planting calendar for 57421
Dates count from your average last spring frost (May 13) and first fall frost (Sep 26). Half of years have a frost after the spring date, so give tender crops (tomatoes, peppers, squash) some slack.
| Crop | Start indoors | Spring planting | Fall planting |
|---|---|---|---|
| Tomato | Mar 18–Apr 1 | May 20–Jun 3 (transplant) | – |
| Pepper (sweet and hot) | Mar 4–18 | May 27–Jun 10 (transplant) | – |
| Eggplant | Mar 4–18 | May 27–Jun 10 (transplant) | – |
| Tomatillo | Mar 18–Apr 1 | May 20–Jun 3 (transplant) | – |
| Lettuce | Mar 18–Apr 1 | Apr 22–May 13 (transplant) Apr 15–May 27 (sow outdoors) | Aug 1–22 (transplant) Jul 18–Aug 15 (sowing) |
| Spinach | – | Apr 1–22 (sow outdoors) | Aug 1–22 (sowing) |
| Kale | Mar 18–Apr 1 | Apr 15–29 (transplant) Apr 15–29 (sow outdoors) | Jul 4–Aug 1 (transplant) Jun 20–Jul 18 (sowing) |
| Collards | Mar 18–Apr 1 | Apr 15–May 13 (transplant) Apr 15–May 13 (sow outdoors) | Jul 4–Aug 1 (transplant) Jun 20–Jul 18 (sowing) |
| Broccoli | Mar 4–18 | Apr 15–29 (transplant) | Jun 20–Jul 18 (transplant) |
| Cabbage | Mar 4–18 | Apr 15–29 (transplant) | Jun 20–Jul 18 (transplant) |
| Cauliflower | Mar 4–18 | Apr 29–May 13 (transplant) | Jun 20–Jul 18 (transplant) |
| Brussels sprouts | Feb 18–Mar 4 | Apr 15–29 (transplant) | Jun 6–27 (transplant) |
| Kohlrabi | Mar 18–Apr 1 | Apr 15–29 (transplant) Apr 15–29 (sow outdoors) | Jul 18–Aug 1 (sowing) |
| Bok choy / Asian greens | – | Apr 15–29 (sow outdoors) | Aug 1–15 (sowing) |
| Arugula | – | Apr 15–May 13 (sow outdoors) | Aug 1–29 (sowing) |
| Mustard greens | – | Apr 15–May 6 (sow outdoors) | Aug 1–15 (sowing) |
| Swiss chard | Apr 1–15 | Apr 29–May 20 (transplant) Apr 29–May 27 (sow outdoors) | Jul 18–Aug 1 (sowing) |
| Beet | – | Apr 15–May 13 (sow outdoors) | Jul 18–Aug 1 (sowing) |
| Carrot | – | Apr 22–May 20 (sow outdoors) | Jul 4–18 (sowing) |
| Radish | – | Apr 8–May 20 (sow outdoors) | Aug 15–29 (sowing) |
| Turnip | – | Apr 15–May 6 (sow outdoors) | Jul 18–Aug 1 (sowing) |
| Parsnip | – | Apr 22–May 13 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Mar 18–Apr 15 (sow outdoors) | Jul 4–18 (sowing) |
| Onion (bulbing) | Feb 18–Mar 4 | Apr 1–15 (transplant) | – |
| Green onion / scallion | – | Apr 1–29 (sow outdoors) | Jul 18–Aug 1 (sowing) |
| Leek | Feb 18–Mar 4 | Apr 15–29 (transplant) | – |
| Garlic | – | – | Aug 15–Sep 12 (sowing) |
| Shallot | – | Apr 1–15 (transplant) | Aug 15–Sep 12 (sowing) |
| Potato | – | Apr 15–29 (transplant) | Jun 6–20 (transplant) |
| Sweet potato | – | Jun 3–17 (transplant) | – |
| Sweet corn | – | May 20–Jun 3 (sow outdoors) | – |
| Bean, bush (snap) | – | May 20–Jun 3 (sow outdoors) | – |
| Bean, pole | – | May 20–Jun 3 (sow outdoors) | – |
| Lima bean | – | May 27–Jun 10 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Jun 3–24 (sow outdoors) | – |
| Cucumber | Apr 15–22 | May 20–Jun 3 (transplant) May 20–Jun 3 (sow outdoors) | – |
| Summer squash / zucchini | Apr 15–22 | May 20–Jun 3 (transplant) May 20–Jun 3 (sow outdoors) | – |
| Winter squash | Apr 15–22 | May 20–Jun 3 (transplant) May 20–Jun 3 (sow outdoors) | – |
| Pumpkin | – | May 20–Jun 3 (sow outdoors) | – |
| Watermelon | Apr 15–22 | May 27–Jun 10 (transplant) May 27–Jun 10 (sow outdoors) | – |
| Cantaloupe / muskmelon | Apr 15–22 | May 27–Jun 10 (transplant) May 27–Jun 10 (sow outdoors) | – |
| Okra | Apr 1–15 | May 27–Jun 10 (transplant) May 27–Jun 10 (sow outdoors) | – |
| Celery | Feb 18–Mar 4 | May 20–27 (transplant) | – |
| Basil | Apr 1–15 | May 20–Jun 3 (transplant) May 20–Jun 3 (sow outdoors) | – |
| Cilantro | – | Apr 29–May 27 (sow outdoors) | Aug 1–15 (sowing) |
| Parsley | Mar 4–18 | Apr 29–May 13 (transplant) Apr 22–May 13 (sow outdoors) | – |
| Dill | – | May 13–27 (sow outdoors) | Aug 1–15 (sowing) |
| Sunflower | – | May 13–27 (sow outdoors) | – |
| Asparagus (crowns) | – | Apr 15–29 (transplant) | – |
| Rhubarb (crowns) | – | Apr 15–29 (transplant) | – |
| Strawberry (plants) | – | Apr 15–29 (transplant) | Jul 18–Aug 15 (transplant) |
Typical ranges from university extension planting calendars, adjusted to your frost dates. Probabilities, not guarantees. Fall windows that would overlap spring planting are left out, as are fall crops of frost-tender plants where the frost-free season is under 210 days.
Where these numbers come from
Station: Britton, SD (NOAA GHCN-Daily ID USC00391049), elevation 1,355 ft, 8.0 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Columbia 8 N, SD | 19 mi | May 7 | Sep 29 |
| Roy Lake, SD | 23 mi | May 2 | Oct 9 |
| Andover #2, SD | 24 mi | May 6 | Oct 4 |
The average last-frost dates of these stations span 11 days, a rough guide to local variation. See data sources & methods.
Frost questions for 57421
When is the last frost in 57421?
The average (50% chance) last spring freeze of 32°F for ZIP 57421 is May 13. For a more cautious planting date, use May 27, when only 1 year in 10 still sees a later freeze.
When is the first frost in 57421?
The average first fall freeze is September 26. In 1 year in 10 it comes by September 14.
What hardiness zone is 57421?
ZIP 57421 is in USDA zone 4a (-30 to -25°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 57421 right now?
This page shows the latest 2-inch and 4-inch soil temperature from the nearest public soil station (USDA SCAN, NOAA USCRN or TexMesonet), or a labeled estimate when no station is close, against the 50–55°F spring pre-emergent band.
Nearby ZIP codes
57432 Newport Colony 57430 Westwood Colony 57454 Langford 57449 57446 Hecla 57468 Pierpont 58017 Cogswell 57433 Columbia
Other ZIP codes in Marshall County
57232 57247 57270 57430 57454 All Marshall County frost dates · South Dakota frost dates
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Weekly yard timing, plus frost and soil-temperature alerts for your ZIP code.
- Freeze alerts
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Free. One weekly email plus alerts when your ZIP has a frost or a soil-temperature change worth acting on. After you submit, Kit (our email provider) sends a confirmation email: check your email and click the link to confirm. You aren't subscribed until you do. We collect only your email address and ZIP, sent to Kit to deliver The Dial. Unsubscribe anytime.