Fall in zone 5aPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 51240 (Inwood, IA)
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, Canton, SD (7 miles away).
- Average last spring frostMay 250% chance of a 32°F freeze after this date
- Average first fall frostOct 250% chance of a 32°F freeze by this date
- Growing season (frost-free)151 daysmedian, 32°F threshold
- USDA hardiness zone5a-20 to -15°F avg. coldest night
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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, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Sioux Falls 14 NNE (30 mi), Eros Data Center (31 mi).
4-inch depth
51°F 50–55°F
24-hour average · latest 52°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Sioux Falls 14 NNE (30 mi), Eros Data Center (31 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 51240 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
Soil is 51°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 19 |
| 50% (the "average" last frost) | May 2 |
| 10% (cautious: only 1 year in 10 freezes later) | May 15 |
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 19 |
| 50% (the "average" first frost) | Oct 2 |
| 90% (late: most years have frozen by now) | Oct 16 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | May 12 | Sep 25 |
| 32°F (freeze) | May 2 | Oct 2 |
| 28°F (hard freeze) | Apr 23 | Oct 11 |
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 51240
Dates count from your average last spring frost (May 2) and first fall frost (Oct 2). 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 7–21 | May 9–23 (transplant) | – |
| Pepper (sweet and hot) | Feb 21–Mar 7 | May 16–30 (transplant) | – |
| Eggplant | Feb 21–Mar 7 | May 16–30 (transplant) | – |
| Tomatillo | Mar 7–21 | May 9–23 (transplant) | – |
| Lettuce | Mar 7–21 | Apr 11–May 2 (transplant) Apr 4–May 16 (sow outdoors) | Aug 7–28 (transplant) Jul 24–Aug 21 (sowing) |
| Spinach | – | Mar 21–Apr 11 (sow outdoors) | Aug 7–28 (sowing) |
| Kale | Mar 7–21 | Apr 4–18 (transplant) Apr 4–18 (sow outdoors) | Jul 10–Aug 7 (transplant) Jun 26–Jul 24 (sowing) |
| Collards | Mar 7–21 | Apr 4–May 2 (transplant) Apr 4–May 2 (sow outdoors) | Jul 10–Aug 7 (transplant) Jun 26–Jul 24 (sowing) |
| Broccoli | Feb 21–Mar 7 | Apr 4–18 (transplant) | Jun 26–Jul 24 (transplant) |
| Cabbage | Feb 21–Mar 7 | Apr 4–18 (transplant) | Jun 26–Jul 24 (transplant) |
| Cauliflower | Feb 21–Mar 7 | Apr 18–May 2 (transplant) | Jun 26–Jul 24 (transplant) |
| Brussels sprouts | Feb 7–21 | Apr 4–18 (transplant) | Jun 12–Jul 3 (transplant) |
| Kohlrabi | Mar 7–21 | Apr 4–18 (transplant) Apr 4–18 (sow outdoors) | Jul 24–Aug 7 (sowing) |
| Bok choy / Asian greens | – | Apr 4–18 (sow outdoors) | Aug 7–21 (sowing) |
| Arugula | – | Apr 4–May 2 (sow outdoors) | Aug 7–Sep 4 (sowing) |
| Mustard greens | – | Apr 4–25 (sow outdoors) | Aug 7–21 (sowing) |
| Swiss chard | Mar 21–Apr 4 | Apr 18–May 9 (transplant) Apr 18–May 16 (sow outdoors) | Jul 24–Aug 7 (sowing) |
| Beet | – | Apr 4–May 2 (sow outdoors) | Jul 24–Aug 7 (sowing) |
| Carrot | – | Apr 11–May 9 (sow outdoors) | Jul 10–24 (sowing) |
| Radish | – | Mar 28–May 9 (sow outdoors) | Aug 21–Sep 4 (sowing) |
| Turnip | – | Apr 4–25 (sow outdoors) | Jul 24–Aug 7 (sowing) |
| Parsnip | – | Apr 11–May 2 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Mar 7–Apr 4 (sow outdoors) | Jul 10–24 (sowing) |
| Onion (bulbing) | Feb 7–21 | Mar 21–Apr 4 (transplant) | – |
| Green onion / scallion | – | Mar 21–Apr 18 (sow outdoors) | Jul 24–Aug 7 (sowing) |
| Leek | Feb 7–21 | Apr 4–18 (transplant) | – |
| Garlic | – | – | Aug 21–Sep 18 (sowing) |
| Shallot | – | Mar 21–Apr 4 (transplant) | Aug 21–Sep 18 (sowing) |
| Potato | – | Apr 4–18 (transplant) | Jun 12–26 (transplant) |
| Sweet potato | – | May 23–Jun 6 (transplant) | – |
| Sweet corn | – | May 9–23 (sow outdoors) | – |
| Bean, bush (snap) | – | May 9–23 (sow outdoors) | – |
| Bean, pole | – | May 9–23 (sow outdoors) | – |
| Lima bean | – | May 16–30 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | May 23–Jun 13 (sow outdoors) | – |
| Cucumber | Apr 4–11 | May 9–23 (transplant) May 9–23 (sow outdoors) | – |
| Summer squash / zucchini | Apr 4–11 | May 9–23 (transplant) May 9–23 (sow outdoors) | – |
| Winter squash | Apr 4–11 | May 9–23 (transplant) May 9–23 (sow outdoors) | – |
| Pumpkin | – | May 9–23 (sow outdoors) | – |
| Watermelon | Apr 4–11 | May 16–30 (transplant) May 16–30 (sow outdoors) | – |
| Cantaloupe / muskmelon | Apr 4–11 | May 16–30 (transplant) May 16–30 (sow outdoors) | – |
| Okra | Mar 21–Apr 4 | May 16–30 (transplant) May 16–30 (sow outdoors) | – |
| Celery | Feb 7–21 | May 9–16 (transplant) | – |
| Basil | Mar 21–Apr 4 | May 9–23 (transplant) May 9–23 (sow outdoors) | – |
| Cilantro | – | Apr 18–May 16 (sow outdoors) | Aug 7–21 (sowing) |
| Parsley | Feb 21–Mar 7 | Apr 18–May 2 (transplant) Apr 11–May 2 (sow outdoors) | – |
| Dill | – | May 2–16 (sow outdoors) | Aug 7–21 (sowing) |
| Sunflower | – | May 2–16 (sow outdoors) | – |
| Asparagus (crowns) | – | Apr 4–18 (transplant) | – |
| Rhubarb (crowns) | – | Apr 4–18 (transplant) | – |
| Strawberry (plants) | – | Apr 4–18 (transplant) | Jul 24–Aug 21 (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: Canton, SD (NOAA GHCN-Daily ID USC00391392), elevation 1,316 ft, 6.5 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Rock Rapids, IA | 17 mi | May 1 | Oct 4 |
| Hawarden, IA | 21 mi | May 1 | Oct 4 |
| Sioux Ctr 2 SE, IA | 23 mi | Apr 30 | Oct 3 |
The average last-frost dates of these stations span 3 days, a rough guide to local variation. See data sources & methods.
Frost questions for 51240
When is the last frost in 51240?
The average (50% chance) last spring freeze of 32°F for ZIP 51240 is May 2. For a more cautious planting date, use May 15, when only 1 year in 10 still sees a later freeze.
When is the first frost in 51240?
The average first fall freeze is October 2. In 1 year in 10 it comes by September 19.
What hardiness zone is 51240?
ZIP 51240 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 51240 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
51230 Alvord 57013 Canton 57027 Fairview 51241 Larchwood 51247 Rock Valley 51242 Lester 51235 Doon 57032 Harrisburg
Other ZIP codes in Lyon County
51230 51235 51237 51241 51242 51243 51246 All Lyon County frost dates · Iowa 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.