Postville, IA frost dates
Last spring frostMay 1median date
First fall frostOct 3median date
Growing season155 daysfrost-free
Hardiness zone5aZone 5a
How Postville compares
- In 8 years out of 10, the last spring frost in Postville falls between April 18 and May 14, a 26-day window. The first fall frost falls between September 20 and October 17.
- The median last frost is 3 days later than the Iowa median of Apr 28.
- Its 155-day growing season is longer than 13% of the 934 Iowa places with a regular frost season (state median 165 days).
- The last frost is typical for zone 5a, where the median is May 3.
- The weather station records an average of 162 nights a year at or below 32°F.
- Compared with Waterloo, IA, 86 km away, the last frost here is 4 days later than there and the growing season is 11 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 18 |
| 50% (median) | May 1 |
| 10% (safe for tender plants) | May 14 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 20 |
| 50% (median) | October 3 |
| 90% (late) | October 17 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Postville, IA
Postville, IA frost dates — last frost May 1, first frost Oct 3, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Feb 6 to Feb 20Transplant outside: Apr 3 to Apr 17
Start indoors: Feb 20 to Mar 6Transplant outside: May 15 to May 29
Start indoors: Feb 20 to Mar 6Transplant outside: May 15 to May 29
Start indoors: Mar 6 to Mar 20Transplant outside: May 8 to May 22
Start indoors: Mar 6 to Mar 20Transplant outside: Apr 10 to Apr 24Sow outdoors: Apr 3 to May 8Plant for fall: Aug 8 to Sep 5
Start indoors: Mar 6 to Mar 20Transplant outside: Apr 3 to Apr 17Sow outdoors: Apr 3 to Apr 17Plant for fall: Jul 25 to Aug 15
Start indoors: Mar 6 to Mar 20Transplant outside: Apr 17 to May 1Plant for fall: Jun 27 to Jul 18
Start indoors: Mar 6 to Mar 20Transplant outside: Apr 10 to Apr 24Plant for fall: Jun 27 to Jul 18
Start indoors: Mar 6 to Mar 20Transplant outside: Apr 17 to May 1Plant for fall: Jun 27 to Jul 18
Start indoors: Mar 20 to Apr 3Transplant outside: May 22 to Jun 5Sow outdoors: May 22 to Jun 5
Start indoors: Mar 20 to Apr 3Transplant outside: May 8 to May 22
Sow outdoors: Mar 20 to Apr 10Plant for fall: Jul 11 to Aug 1
Sow outdoors: Mar 20 to Apr 10Plant for fall: Aug 8 to Aug 29
Sow outdoors: Mar 27 to May 8Plant for fall: Aug 22 to Sep 12
Start indoors: Apr 3 to Apr 10Transplant outside: May 15 to May 22Sow outdoors: May 8 to May 22Plant for fall: Jul 18 to Aug 1
Start indoors: Apr 3 to Apr 10Sow outdoors: May 8 to May 22Plant for fall: Jul 25 to Aug 8
Start indoors: Apr 3 to Apr 10Sow outdoors: May 8 to May 22
Start indoors: Apr 3 to Apr 10Transplant outside: May 15 to May 29
Sow outdoors: Apr 10 to May 8Plant for fall: Jul 11 to Jul 25
Sow outdoors: Apr 10 to May 8Plant for fall: Jul 25 to Aug 8
Sow outdoors: Apr 10 to May 1
Sow outdoors: Apr 17 to May 15Plant for fall: Jul 25 to Aug 8
Sow outdoors: Apr 17 to May 8Plant for fall: Aug 8 to Aug 29
Sow outdoors: May 8 to May 29Plant for fall: Jul 18 to Aug 1
Sow outdoors: May 8 to May 22
Transplant outside: May 15 to Jun 5
Plant for fall: Sep 19 to Oct 24
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Postville, IA
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 6 – Feb 20 | Apr 3 – Apr 17 | — | — |
| Peppers | Feb 20 – Mar 6 | May 15 – May 29 | — | — |
| Eggplant | Feb 20 – Mar 6 | May 15 – May 29 | — | — |
| Tomatoes | Mar 6 – Mar 20 | May 8 – May 22 | — | — |
| Lettuce | Mar 6 – Mar 20 | Apr 10 – Apr 24 | Apr 3 – May 8 | Aug 8 – Sep 5 |
| Kale | Mar 6 – Mar 20 | Apr 3 – Apr 17 | Apr 3 – Apr 17 | Jul 25 – Aug 15 |
| Broccoli | Mar 6 – Mar 20 | Apr 17 – May 1 | — | Jun 27 – Jul 18 |
| Cabbage | Mar 6 – Mar 20 | Apr 10 – Apr 24 | — | Jun 27 – Jul 18 |
| Cauliflower | Mar 6 – Mar 20 | Apr 17 – May 1 | — | Jun 27 – Jul 18 |
| Okra | Mar 20 – Apr 3 | May 22 – Jun 5 | May 22 – Jun 5 | — |
| Basil | Mar 20 – Apr 3 | May 8 – May 22 | — | — |
| Peas | — | — | Mar 20 – Apr 10 | Jul 11 – Aug 1 |
| Spinach | — | — | Mar 20 – Apr 10 | Aug 8 – Aug 29 |
| Radishes | — | — | Mar 27 – May 8 | Aug 22 – Sep 12 |
| Cucumbers | Apr 3 – Apr 10 | May 15 – May 22 | May 8 – May 22 | Jul 18 – Aug 1 |
| Zucchini & Summer Squash | Apr 3 – Apr 10 | — | May 8 – May 22 | Jul 25 – Aug 8 |
| Winter Squash & Pumpkins | Apr 3 – Apr 10 | — | May 8 – May 22 | — |
| Melons & Watermelon | Apr 3 – Apr 10 | May 15 – May 29 | — | — |
| Carrots | — | — | Apr 10 – May 8 | Jul 11 – Jul 25 |
| Beets | — | — | Apr 10 – May 8 | Jul 25 – Aug 8 |
| Potatoes | — | — | Apr 10 – May 1 | — |
| Swiss Chard | — | — | Apr 17 – May 15 | Jul 25 – Aug 8 |
| Cilantro | — | — | Apr 17 – May 8 | Aug 8 – Aug 29 |
| Green Beans | — | — | May 8 – May 29 | Jul 18 – Aug 1 |
| Sweet Corn | — | — | May 8 – May 22 | — |
| Sweet Potatoes | — | May 15 – Jun 5 | — | — |
| Garlic | — | — | — | Sep 19 – Oct 24 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Postville, IA weather station, 10 km away (elevation 1,165 ft (355 m)).
Frost dates near Postville
- Clermont May 1 · Oct 3
- Luana May 1 · Oct 3
- Elgin May 1 · Oct 3
- Monona May 1 · Oct 3
- Saint Olaf May 8 · Oct 1
- Castalia May 1 · Oct 3
- Farmersburg Apr 28 · Oct 12
- Wadena May 4 · Oct 4
- Elkader May 8 · Oct 1
- Ossian May 1 · Oct 3
Frequently asked questions
When is the last frost in Postville, IA?
The median last spring frost in Postville, IA is May 1. There is still about a 10% chance of frost after May 14, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Postville, IA?
The median first fall frost is October 3, with about a 10% chance of frost before September 20.
How long is the growing season in Postville, IA?
About 155 days between the median last spring frost and first fall frost.
What planting zone is Postville, IA?
Postville, IA is in USDA hardiness zone 5a.