Fall in zone 5bPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 50021 (Ankeny, 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, Ankeny, IA (4 miles away).
- Average last spring frostApr 2350% chance of a 32°F freeze after this date
- Average first fall frostOct 1550% chance of a 32°F freeze by this date
- Growing season (frost-free)173 daysmedian, 32°F threshold
- USDA hardiness zone5b-15 to -10°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
56°F 55°F or warmer
24-hour average · latest 56°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Des Moines 17 E (18 mi), Ames (22 mi).
4-inch depth
57°F 55°F or warmer
24-hour average · latest 57°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Des Moines 17 E (18 mi), Ames (22 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 50021 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
Soil is 57°F at 4 inches (estimated soil temperature, not a station reading). Fall pre-emergent (annual bluegrass, winter weeds): window open as soil cools through the 70s and 60s.
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 8 |
| 50% (the "average" last frost) | Apr 23 |
| 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 30 |
| 50% (the "average" first frost) | Oct 15 |
| 90% (late: most years have frozen by now) | Oct 28 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | May 3 | Oct 4 |
| 32°F (freeze) | Apr 23 | Oct 15 |
| 28°F (hard freeze) | Apr 13 | Oct 25 |
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 50021
Dates count from your average last spring frost (Apr 23) and first fall frost (Oct 15). 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 | Feb 26–Mar 12 | Apr 30–May 14 (transplant) | – |
| Pepper (sweet and hot) | Feb 12–26 | May 7–21 (transplant) | – |
| Eggplant | Feb 12–26 | May 7–21 (transplant) | – |
| Tomatillo | Feb 26–Mar 12 | Apr 30–May 14 (transplant) | – |
| Lettuce | Feb 26–Mar 12 | Apr 2–23 (transplant) Mar 26–May 7 (sow outdoors) | Aug 20–Sep 10 (transplant) Aug 6–Sep 3 (sowing) |
| Spinach | – | Mar 12–Apr 2 (sow outdoors) | Aug 20–Sep 10 (sowing) |
| Kale | Feb 26–Mar 12 | Mar 26–Apr 9 (transplant) Mar 26–Apr 9 (sow outdoors) | Jul 23–Aug 20 (transplant) Jul 9–Aug 6 (sowing) |
| Collards | Feb 26–Mar 12 | Mar 26–Apr 23 (transplant) Mar 26–Apr 23 (sow outdoors) | Jul 23–Aug 20 (transplant) Jul 9–Aug 6 (sowing) |
| Broccoli | Feb 12–26 | Mar 26–Apr 9 (transplant) | Jul 9–Aug 6 (transplant) |
| Cabbage | Feb 12–26 | Mar 26–Apr 9 (transplant) | Jul 9–Aug 6 (transplant) |
| Cauliflower | Feb 12–26 | Apr 9–23 (transplant) | Jul 9–Aug 6 (transplant) |
| Brussels sprouts | Jan 29–Feb 12 | Mar 26–Apr 9 (transplant) | Jun 25–Jul 16 (transplant) |
| Kohlrabi | Feb 26–Mar 12 | Mar 26–Apr 9 (transplant) Mar 26–Apr 9 (sow outdoors) | Aug 6–20 (sowing) |
| Bok choy / Asian greens | – | Mar 26–Apr 9 (sow outdoors) | Aug 20–Sep 3 (sowing) |
| Arugula | – | Mar 26–Apr 23 (sow outdoors) | Aug 20–Sep 17 (sowing) |
| Mustard greens | – | Mar 26–Apr 16 (sow outdoors) | Aug 20–Sep 3 (sowing) |
| Swiss chard | Mar 12–26 | Apr 9–30 (transplant) Apr 9–May 7 (sow outdoors) | Aug 6–20 (sowing) |
| Beet | – | Mar 26–Apr 23 (sow outdoors) | Aug 6–20 (sowing) |
| Carrot | – | Apr 2–30 (sow outdoors) | Jul 23–Aug 6 (sowing) |
| Radish | – | Mar 19–Apr 30 (sow outdoors) | Sep 3–17 (sowing) |
| Turnip | – | Mar 26–Apr 16 (sow outdoors) | Aug 6–20 (sowing) |
| Parsnip | – | Apr 2–23 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Feb 26–Mar 26 (sow outdoors) | Jul 23–Aug 6 (sowing) |
| Onion (bulbing) | Jan 29–Feb 12 | Mar 12–26 (transplant) | – |
| Green onion / scallion | – | Mar 12–Apr 9 (sow outdoors) | Aug 6–20 (sowing) |
| Leek | Jan 29–Feb 12 | Mar 26–Apr 9 (transplant) | – |
| Garlic | – | – | Sep 3–Oct 1 (sowing) |
| Shallot | – | Mar 12–26 (transplant) | Sep 3–Oct 1 (sowing) |
| Potato | – | Mar 26–Apr 9 (transplant) | Jun 25–Jul 9 (transplant) |
| Sweet potato | – | May 14–28 (transplant) | – |
| Sweet corn | – | Apr 30–May 14 (sow outdoors) | – |
| Bean, bush (snap) | – | Apr 30–May 14 (sow outdoors) | – |
| Bean, pole | – | Apr 30–May 14 (sow outdoors) | – |
| Lima bean | – | May 7–21 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | May 14–Jun 4 (sow outdoors) | – |
| Cucumber | Mar 26–Apr 2 | Apr 30–May 14 (transplant) Apr 30–May 14 (sow outdoors) | – |
| Summer squash / zucchini | Mar 26–Apr 2 | Apr 30–May 14 (transplant) Apr 30–May 14 (sow outdoors) | – |
| Winter squash | Mar 26–Apr 2 | Apr 30–May 14 (transplant) Apr 30–May 14 (sow outdoors) | – |
| Pumpkin | – | Apr 30–May 14 (sow outdoors) | – |
| Watermelon | Mar 26–Apr 2 | May 7–21 (transplant) May 7–21 (sow outdoors) | – |
| Cantaloupe / muskmelon | Mar 26–Apr 2 | May 7–21 (transplant) May 7–21 (sow outdoors) | – |
| Okra | Mar 12–26 | May 7–21 (transplant) May 7–21 (sow outdoors) | – |
| Celery | Jan 29–Feb 12 | Apr 30–May 7 (transplant) | – |
| Basil | Mar 12–26 | Apr 30–May 14 (transplant) Apr 30–May 14 (sow outdoors) | – |
| Cilantro | – | Apr 9–May 7 (sow outdoors) | Aug 20–Sep 3 (sowing) |
| Parsley | Feb 12–26 | Apr 9–23 (transplant) Apr 2–23 (sow outdoors) | – |
| Dill | – | Apr 23–May 7 (sow outdoors) | Aug 20–Sep 3 (sowing) |
| Sunflower | – | Apr 23–May 7 (sow outdoors) | – |
| Asparagus (crowns) | – | Mar 26–Apr 9 (transplant) | – |
| Rhubarb (crowns) | – | Mar 26–Apr 9 (transplant) | – |
| Strawberry (plants) | – | Mar 26–Apr 9 (transplant) | Aug 6–Sep 3 (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: Ankeny, IA (NOAA GHCN-Daily ID USC00130241), elevation 975 ft, 4.4 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Des Moines Wsfo-johnston, IA | 8 mi | Apr 19 | Oct 18 |
| Des Moines Intl AP, IA | 14 mi | Apr 18 | Oct 20 |
| Ames 5 SE, IA | 16 mi | Apr 26 | Oct 12 |
The average last-frost dates of these stations span 8 days, a rough guide to local variation. See data sources & methods.
Frost questions for 50021
When is the last frost in 50021?
The average (50% chance) last spring freeze of 32°F for ZIP 50021 is April 23. 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 50021?
The average first fall freeze is October 15. In 1 year in 10 it comes by September 30.
What hardiness zone is 50021?
ZIP 50021 is in USDA zone 5b (-15 to -10°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 50021 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
50023 Ankeny 50032 50073 Elkhart 50035 Bondurant 50313 Des Moines 50007 Alleman 50317 Des Moines 50009 Altoona
Other ZIP codes in Polk County
50007 50009 50023 50032 50035 50073 50109 50111 50131 50161 50169 50226 50237 50243 50244 50265 50309 50310 50311 50312 50313 50314 50315 50316 All Polk 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.