Fall in zone 5aPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 50552 (Knierim, 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, Rockwell City, IA (10 miles away).
- Average last spring frostApr 2650% chance of a 32°F freeze after this date
- Average first fall frostOct 1050% chance of a 32°F freeze by this date
- Growing season (frost-free)167 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
53°F 50–55°F
24-hour average · latest 54°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Ames (48 mi).
4-inch depth
55°F 50–55°F
24-hour average · latest 55°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Ames (48 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 50552 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
Soil is 55°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 11 |
| 50% (the "average" last frost) | Apr 26 |
| 10% (cautious: only 1 year in 10 freezes later) | May 6 |
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 27 |
| 50% (the "average" first frost) | Oct 10 |
| 90% (late: most years have frozen by now) | Oct 24 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | May 4 | Oct 1 |
| 32°F (freeze) | Apr 26 | Oct 10 |
| 28°F (hard freeze) | Apr 16 | Oct 21 |
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 50552
Dates count from your average last spring frost (Apr 26) and first fall frost (Oct 10). 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 1–15 | May 3–17 (transplant) | – |
| Pepper (sweet and hot) | Feb 15–Mar 1 | May 10–24 (transplant) | – |
| Eggplant | Feb 15–Mar 1 | May 10–24 (transplant) | – |
| Tomatillo | Mar 1–15 | May 3–17 (transplant) | – |
| Lettuce | Mar 1–15 | Apr 5–26 (transplant) Mar 29–May 10 (sow outdoors) | Aug 15–Sep 5 (transplant) Aug 1–29 (sowing) |
| Spinach | – | Mar 15–Apr 5 (sow outdoors) | Aug 15–Sep 5 (sowing) |
| Kale | Mar 1–15 | Mar 29–Apr 12 (transplant) Mar 29–Apr 12 (sow outdoors) | Jul 18–Aug 15 (transplant) Jul 4–Aug 1 (sowing) |
| Collards | Mar 1–15 | Mar 29–Apr 26 (transplant) Mar 29–Apr 26 (sow outdoors) | Jul 18–Aug 15 (transplant) Jul 4–Aug 1 (sowing) |
| Broccoli | Feb 15–Mar 1 | Mar 29–Apr 12 (transplant) | Jul 4–Aug 1 (transplant) |
| Cabbage | Feb 15–Mar 1 | Mar 29–Apr 12 (transplant) | Jul 4–Aug 1 (transplant) |
| Cauliflower | Feb 15–Mar 1 | Apr 12–26 (transplant) | Jul 4–Aug 1 (transplant) |
| Brussels sprouts | Feb 1–15 | Mar 29–Apr 12 (transplant) | Jun 20–Jul 11 (transplant) |
| Kohlrabi | Mar 1–15 | Mar 29–Apr 12 (transplant) Mar 29–Apr 12 (sow outdoors) | Aug 1–15 (sowing) |
| Bok choy / Asian greens | – | Mar 29–Apr 12 (sow outdoors) | Aug 15–29 (sowing) |
| Arugula | – | Mar 29–Apr 26 (sow outdoors) | Aug 15–Sep 12 (sowing) |
| Mustard greens | – | Mar 29–Apr 19 (sow outdoors) | Aug 15–29 (sowing) |
| Swiss chard | Mar 15–29 | Apr 12–May 3 (transplant) Apr 12–May 10 (sow outdoors) | Aug 1–15 (sowing) |
| Beet | – | Mar 29–Apr 26 (sow outdoors) | Aug 1–15 (sowing) |
| Carrot | – | Apr 5–May 3 (sow outdoors) | Jul 18–Aug 1 (sowing) |
| Radish | – | Mar 22–May 3 (sow outdoors) | Aug 29–Sep 12 (sowing) |
| Turnip | – | Mar 29–Apr 19 (sow outdoors) | Aug 1–15 (sowing) |
| Parsnip | – | Apr 5–26 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Mar 1–29 (sow outdoors) | Jul 18–Aug 1 (sowing) |
| Onion (bulbing) | Feb 1–15 | Mar 15–29 (transplant) | – |
| Green onion / scallion | – | Mar 15–Apr 12 (sow outdoors) | Aug 1–15 (sowing) |
| Leek | Feb 1–15 | Mar 29–Apr 12 (transplant) | – |
| Garlic | – | – | Aug 29–Sep 26 (sowing) |
| Shallot | – | Mar 15–29 (transplant) | Aug 29–Sep 26 (sowing) |
| Potato | – | Mar 29–Apr 12 (transplant) | Jun 20–Jul 4 (transplant) |
| Sweet potato | – | May 17–31 (transplant) | – |
| Sweet corn | – | May 3–17 (sow outdoors) | – |
| Bean, bush (snap) | – | May 3–17 (sow outdoors) | – |
| Bean, pole | – | May 3–17 (sow outdoors) | – |
| Lima bean | – | May 10–24 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | May 17–Jun 7 (sow outdoors) | – |
| Cucumber | Mar 29–Apr 5 | May 3–17 (transplant) May 3–17 (sow outdoors) | – |
| Summer squash / zucchini | Mar 29–Apr 5 | May 3–17 (transplant) May 3–17 (sow outdoors) | – |
| Winter squash | Mar 29–Apr 5 | May 3–17 (transplant) May 3–17 (sow outdoors) | – |
| Pumpkin | – | May 3–17 (sow outdoors) | – |
| Watermelon | Mar 29–Apr 5 | May 10–24 (transplant) May 10–24 (sow outdoors) | – |
| Cantaloupe / muskmelon | Mar 29–Apr 5 | May 10–24 (transplant) May 10–24 (sow outdoors) | – |
| Okra | Mar 15–29 | May 10–24 (transplant) May 10–24 (sow outdoors) | – |
| Celery | Feb 1–15 | May 3–10 (transplant) | – |
| Basil | Mar 15–29 | May 3–17 (transplant) May 3–17 (sow outdoors) | – |
| Cilantro | – | Apr 12–May 10 (sow outdoors) | Aug 15–29 (sowing) |
| Parsley | Feb 15–Mar 1 | Apr 12–26 (transplant) Apr 5–26 (sow outdoors) | – |
| Dill | – | Apr 26–May 10 (sow outdoors) | Aug 15–29 (sowing) |
| Sunflower | – | Apr 26–May 10 (sow outdoors) | – |
| Asparagus (crowns) | – | Mar 29–Apr 12 (transplant) | – |
| Rhubarb (crowns) | – | Mar 29–Apr 12 (transplant) | – |
| Strawberry (plants) | – | Mar 29–Apr 12 (transplant) | Aug 1–29 (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: Rockwell City, IA (NOAA GHCN-Daily ID USC00137161), elevation 1,214 ft, 9.5 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Ft Dodge 5NNW, IA | 16 mi | Apr 28 | Oct 8 |
| Pocahontas, IA | 21 mi | Apr 26 | Oct 7 |
| Humboldt WTP, IA | 22 mi | Apr 27 | Oct 9 |
The average last-frost dates of these stations span 2 days, a rough guide to local variation. See data sources & methods.
Frost questions for 50552
When is the last frost in 50552?
The average (50% chance) last spring freeze of 32°F for ZIP 50552 is April 26. For a more cautious planting date, use May 6, when only 1 year in 10 still sees a later freeze.
When is the first frost in 50552?
The average first fall freeze is October 10. In 1 year in 10 it comes by September 27.
What hardiness zone is 50552?
ZIP 50552 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 50552 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
50586 Somers 50518 Barnum 50563 Manson 50566 Moorland 50579 Rockwell City 50523 Callender 50524 Clare 50538 Rinard
Other ZIP codes in Calhoun County
50538 50551 50561 50563 50575 50579 50586 51449 51453 All Calhoun County frost dates · Iowa frost dates
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Weekly yard timing, plus frost and soil-temperature alerts for your ZIP code.
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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.