Fall in zone 5aPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 52133 (Castalia, 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, Postville, IA (5 miles away).
- Average last spring frostMay 150% chance of a 32°F freeze after this date
- Average first fall frostOct 350% chance of a 32°F freeze by this date
- Growing season (frost-free)153 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
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 52133 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) | Apr 18 |
| 50% (the "average" last frost) | May 1 |
| 10% (cautious: only 1 year in 10 freezes later) | May 14 |
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 20 |
| 50% (the "average" first frost) | Oct 3 |
| 90% (late: most years have frozen by now) | Oct 17 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | May 10 | Sep 24 |
| 32°F (freeze) | May 1 | Oct 3 |
| 28°F (hard freeze) | Apr 22 | Oct 12 |
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 52133
Dates count from your average last spring frost (May 1) and first fall frost (Oct 3). 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 6–20 | May 8–22 (transplant) | – |
| Pepper (sweet and hot) | Feb 20–Mar 6 | May 15–29 (transplant) | – |
| Eggplant | Feb 20–Mar 6 | May 15–29 (transplant) | – |
| Tomatillo | Mar 6–20 | May 8–22 (transplant) | – |
| Lettuce | Mar 6–20 | Apr 10–May 1 (transplant) Apr 3–May 15 (sow outdoors) | Aug 8–29 (transplant) Jul 25–Aug 22 (sowing) |
| Spinach | – | Mar 20–Apr 10 (sow outdoors) | Aug 8–29 (sowing) |
| Kale | Mar 6–20 | Apr 3–17 (transplant) Apr 3–17 (sow outdoors) | Jul 11–Aug 8 (transplant) Jun 27–Jul 25 (sowing) |
| Collards | Mar 6–20 | Apr 3–May 1 (transplant) Apr 3–May 1 (sow outdoors) | Jul 11–Aug 8 (transplant) Jun 27–Jul 25 (sowing) |
| Broccoli | Feb 20–Mar 6 | Apr 3–17 (transplant) | Jun 27–Jul 25 (transplant) |
| Cabbage | Feb 20–Mar 6 | Apr 3–17 (transplant) | Jun 27–Jul 25 (transplant) |
| Cauliflower | Feb 20–Mar 6 | Apr 17–May 1 (transplant) | Jun 27–Jul 25 (transplant) |
| Brussels sprouts | Feb 6–20 | Apr 3–17 (transplant) | Jun 13–Jul 4 (transplant) |
| Kohlrabi | Mar 6–20 | Apr 3–17 (transplant) Apr 3–17 (sow outdoors) | Jul 25–Aug 8 (sowing) |
| Bok choy / Asian greens | – | Apr 3–17 (sow outdoors) | Aug 8–22 (sowing) |
| Arugula | – | Apr 3–May 1 (sow outdoors) | Aug 8–Sep 5 (sowing) |
| Mustard greens | – | Apr 3–24 (sow outdoors) | Aug 8–22 (sowing) |
| Swiss chard | Mar 20–Apr 3 | Apr 17–May 8 (transplant) Apr 17–May 15 (sow outdoors) | Jul 25–Aug 8 (sowing) |
| Beet | – | Apr 3–May 1 (sow outdoors) | Jul 25–Aug 8 (sowing) |
| Carrot | – | Apr 10–May 8 (sow outdoors) | Jul 11–25 (sowing) |
| Radish | – | Mar 27–May 8 (sow outdoors) | Aug 22–Sep 5 (sowing) |
| Turnip | – | Apr 3–24 (sow outdoors) | Jul 25–Aug 8 (sowing) |
| Parsnip | – | Apr 10–May 1 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Mar 6–Apr 3 (sow outdoors) | Jul 11–25 (sowing) |
| Onion (bulbing) | Feb 6–20 | Mar 20–Apr 3 (transplant) | – |
| Green onion / scallion | – | Mar 20–Apr 17 (sow outdoors) | Jul 25–Aug 8 (sowing) |
| Leek | Feb 6–20 | Apr 3–17 (transplant) | – |
| Garlic | – | – | Aug 22–Sep 19 (sowing) |
| Shallot | – | Mar 20–Apr 3 (transplant) | Aug 22–Sep 19 (sowing) |
| Potato | – | Apr 3–17 (transplant) | Jun 13–27 (transplant) |
| Sweet potato | – | May 22–Jun 5 (transplant) | – |
| Sweet corn | – | May 8–22 (sow outdoors) | – |
| Bean, bush (snap) | – | May 8–22 (sow outdoors) | – |
| Bean, pole | – | May 8–22 (sow outdoors) | – |
| Lima bean | – | May 15–29 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | May 22–Jun 12 (sow outdoors) | – |
| Cucumber | Apr 3–10 | May 8–22 (transplant) May 8–22 (sow outdoors) | – |
| Summer squash / zucchini | Apr 3–10 | May 8–22 (transplant) May 8–22 (sow outdoors) | – |
| Winter squash | Apr 3–10 | May 8–22 (transplant) May 8–22 (sow outdoors) | – |
| Pumpkin | – | May 8–22 (sow outdoors) | – |
| Watermelon | Apr 3–10 | May 15–29 (transplant) May 15–29 (sow outdoors) | – |
| Cantaloupe / muskmelon | Apr 3–10 | May 15–29 (transplant) May 15–29 (sow outdoors) | – |
| Okra | Mar 20–Apr 3 | May 15–29 (transplant) May 15–29 (sow outdoors) | – |
| Celery | Feb 6–20 | May 8–15 (transplant) | – |
| Basil | Mar 20–Apr 3 | May 8–22 (transplant) May 8–22 (sow outdoors) | – |
| Cilantro | – | Apr 17–May 15 (sow outdoors) | Aug 8–22 (sowing) |
| Parsley | Feb 20–Mar 6 | Apr 17–May 1 (transplant) Apr 10–May 1 (sow outdoors) | – |
| Dill | – | May 1–15 (sow outdoors) | Aug 8–22 (sowing) |
| Sunflower | – | May 1–15 (sow outdoors) | – |
| Asparagus (crowns) | – | Apr 3–17 (transplant) | – |
| Rhubarb (crowns) | – | Apr 3–17 (transplant) | – |
| Strawberry (plants) | – | Apr 3–17 (transplant) | Jul 25–Aug 22 (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: Postville, IA (NOAA GHCN-Daily ID USC00136766), elevation 1,165 ft, 5.3 miles from the ZIP's center point. NOAA completeness flag: R (representative, 10+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Waukon, IA | 15 mi | May 2 | Oct 11 |
| Decorah, IA | 15 mi | May 3 | Oct 7 |
| Fayette, IA | 18 mi | May 4 | Oct 4 |
The average last-frost dates of these stations span 3 days, a rough guide to local variation. See data sources & methods.
Frost questions for 52133
When is the last frost in 52133?
The average (50% chance) last spring freeze of 32°F for ZIP 52133 is May 1. For a more cautious planting date, use May 14, when only 1 year in 10 still sees a later freeze.
When is the first frost in 52133?
The average first fall freeze is October 3. In 1 year in 10 it comes by September 20.
What hardiness zone is 52133?
ZIP 52133 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 52133 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
52161 Ossian 52162 Postville 52135 Clermont 52156 Luana 52175 West Union 52141 Elgin 52166 St. Lucas 52172 Waukon
Other ZIP codes in Winneshiek County
52101 52132 52144 52161 52165 52168 All Winneshiek County frost dates · Iowa frost dates
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