Fall in zone 5aPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 57751 (Keystone, 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, Mt Rushmore Nmem, SD (2 miles away).
- Average last spring frostMay 1550% chance of a 32°F freeze after this date
- Average first fall frostOct 150% chance of a 32°F freeze by this date
- Growing season (frost-free)138 daysmedian, 32°F threshold
- USDA hardiness zone5a-20 to -15°F avg. coldest night
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Frost and freeze alerts from the NWS forecast for 57751, 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
No soil station with a fresh reading within 62 miles.
4-inch depth
No soil station with a fresh reading within 62 miles.
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 57751 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
No soil reading near this ZIP. Typical extension timing for your region: spring 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) | May 1 |
| 50% (the "average" last frost) | May 15 |
| 10% (cautious: only 1 year in 10 freezes later) | May 29 |
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 16 |
| 50% (the "average" first frost) | Oct 1 |
| 90% (late: most years have frozen by now) | Oct 19 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | May 25 | Sep 25 |
| 32°F (freeze) | May 15 | Oct 1 |
| 28°F (hard freeze) | May 4 | Oct 10 |
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 57751
Dates count from your average last spring frost (May 15) and first fall frost (Oct 1). 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 20–Apr 3 | May 22–Jun 5 (transplant) | – |
| Pepper (sweet and hot) | Mar 6–20 | May 29–Jun 12 (transplant) | – |
| Eggplant | Mar 6–20 | May 29–Jun 12 (transplant) | – |
| Tomatillo | Mar 20–Apr 3 | May 22–Jun 5 (transplant) | – |
| Lettuce | Mar 20–Apr 3 | Apr 24–May 15 (transplant) Apr 17–May 29 (sow outdoors) | Aug 6–27 (transplant) Jul 23–Aug 20 (sowing) |
| Spinach | – | Apr 3–24 (sow outdoors) | Aug 6–27 (sowing) |
| Kale | Mar 20–Apr 3 | Apr 17–May 1 (transplant) Apr 17–May 1 (sow outdoors) | Jul 9–Aug 6 (transplant) Jun 25–Jul 23 (sowing) |
| Collards | Mar 20–Apr 3 | Apr 17–May 15 (transplant) Apr 17–May 15 (sow outdoors) | Jul 9–Aug 6 (transplant) Jun 25–Jul 23 (sowing) |
| Broccoli | Mar 6–20 | Apr 17–May 1 (transplant) | Jun 25–Jul 23 (transplant) |
| Cabbage | Mar 6–20 | Apr 17–May 1 (transplant) | Jun 25–Jul 23 (transplant) |
| Cauliflower | Mar 6–20 | May 1–15 (transplant) | Jun 25–Jul 23 (transplant) |
| Brussels sprouts | Feb 20–Mar 6 | Apr 17–May 1 (transplant) | Jun 11–Jul 2 (transplant) |
| Kohlrabi | Mar 20–Apr 3 | Apr 17–May 1 (transplant) Apr 17–May 1 (sow outdoors) | Jul 23–Aug 6 (sowing) |
| Bok choy / Asian greens | – | Apr 17–May 1 (sow outdoors) | Aug 6–20 (sowing) |
| Arugula | – | Apr 17–May 15 (sow outdoors) | Aug 6–Sep 3 (sowing) |
| Mustard greens | – | Apr 17–May 8 (sow outdoors) | Aug 6–20 (sowing) |
| Swiss chard | Apr 3–17 | May 1–22 (transplant) May 1–29 (sow outdoors) | Jul 23–Aug 6 (sowing) |
| Beet | – | Apr 17–May 15 (sow outdoors) | Jul 23–Aug 6 (sowing) |
| Carrot | – | Apr 24–May 22 (sow outdoors) | Jul 9–23 (sowing) |
| Radish | – | Apr 10–May 22 (sow outdoors) | Aug 20–Sep 3 (sowing) |
| Turnip | – | Apr 17–May 8 (sow outdoors) | Jul 23–Aug 6 (sowing) |
| Parsnip | – | Apr 24–May 15 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Mar 20–Apr 17 (sow outdoors) | Jul 9–23 (sowing) |
| Onion (bulbing) | Feb 20–Mar 6 | Apr 3–17 (transplant) | – |
| Green onion / scallion | – | Apr 3–May 1 (sow outdoors) | Jul 23–Aug 6 (sowing) |
| Leek | Feb 20–Mar 6 | Apr 17–May 1 (transplant) | – |
| Garlic | – | – | Aug 20–Sep 17 (sowing) |
| Shallot | – | Apr 3–17 (transplant) | Aug 20–Sep 17 (sowing) |
| Potato | – | Apr 17–May 1 (transplant) | Jun 11–25 (transplant) |
| Sweet potato | – | Jun 5–19 (transplant) | – |
| Sweet corn | – | May 22–Jun 5 (sow outdoors) | – |
| Bean, bush (snap) | – | May 22–Jun 5 (sow outdoors) | – |
| Bean, pole | – | May 22–Jun 5 (sow outdoors) | – |
| Lima bean | – | May 29–Jun 12 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | Jun 5–26 (sow outdoors) | – |
| Cucumber | Apr 17–24 | May 22–Jun 5 (transplant) May 22–Jun 5 (sow outdoors) | – |
| Summer squash / zucchini | Apr 17–24 | May 22–Jun 5 (transplant) May 22–Jun 5 (sow outdoors) | – |
| Winter squash | Apr 17–24 | May 22–Jun 5 (transplant) May 22–Jun 5 (sow outdoors) | – |
| Pumpkin | – | May 22–Jun 5 (sow outdoors) | – |
| Watermelon | Apr 17–24 | May 29–Jun 12 (transplant) May 29–Jun 12 (sow outdoors) | – |
| Cantaloupe / muskmelon | Apr 17–24 | May 29–Jun 12 (transplant) May 29–Jun 12 (sow outdoors) | – |
| Okra | Apr 3–17 | May 29–Jun 12 (transplant) May 29–Jun 12 (sow outdoors) | – |
| Celery | Feb 20–Mar 6 | May 22–29 (transplant) | – |
| Basil | Apr 3–17 | May 22–Jun 5 (transplant) May 22–Jun 5 (sow outdoors) | – |
| Cilantro | – | May 1–29 (sow outdoors) | Aug 6–20 (sowing) |
| Parsley | Mar 6–20 | May 1–15 (transplant) Apr 24–May 15 (sow outdoors) | – |
| Dill | – | May 15–29 (sow outdoors) | Aug 6–20 (sowing) |
| Sunflower | – | May 15–29 (sow outdoors) | – |
| Asparagus (crowns) | – | Apr 17–May 1 (transplant) | – |
| Rhubarb (crowns) | – | Apr 17–May 1 (transplant) | – |
| Strawberry (plants) | – | Apr 17–May 1 (transplant) | Jul 23–Aug 20 (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: Mt Rushmore Nmem, SD (NOAA GHCN-Daily ID USC00395870), elevation 5,311 ft, 1.6 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Hill City, SD | 8 mi | Jun 1 | Sep 10 |
| Custer, SD | 11 mi | May 18 | Sep 28 |
| Custer Co AP, SD | 13 mi | May 23 | Sep 24 |
The average last-frost dates of these stations span 17 days, a rough guide to local variation. See data sources & methods.
Frost questions for 57751
When is the last frost in 57751?
The average (50% chance) last spring freeze of 32°F for ZIP 57751 is May 15. For a more cautious planting date, use May 29, when only 1 year in 10 still sees a later freeze.
When is the first frost in 57751?
The average first fall freeze is October 1. In 1 year in 10 it comes by September 16.
What hardiness zone is 57751?
ZIP 57751 is in USDA zone 5a (-20 to -15°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 57751 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
57702 Rapid City 57730 Custer 57738 Fairburn 57744 Hermosa 57745 Hill City 57773 Pringle 57701 Rapid City 57718 Blackhawk
Other ZIP codes in Pennington County
57701 57702 57703 57725 57745 57775 57780 57790 All Pennington 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.