Decatur, IA frost dates
Last spring frostApr 16median date
First fall frostOct 21median date
Growing season188 daysfrost-free
Hardiness zone5bZone 5b
How Decatur compares
- In 8 years out of 10, the last spring frost in Decatur falls between April 2 and May 2, a 30-day window. The first fall frost falls between October 6 and November 1.
- The median last frost is 12 days earlier than the Iowa median of Apr 28.
- Its 188-day growing season is longer than 96% of the 934 Iowa places with a regular frost season (state median 165 days).
- The last frost is 15 days earlier than the zone 5b median of May 1. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5b chart.
- The weather station records an average of 125 nights a year at or below 32°F.
- Compared with West Des Moines, IA, 93 km away, the last frost here is 2 days earlier than there and the growing season is 3 days longer.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 2 |
| 50% (median) | April 16 |
| 10% (safe for tender plants) | May 2 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 6 |
| 50% (median) | October 21 |
| 90% (late) | November 1 |
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 Decatur, IA
Decatur, IA frost dates — last frost Apr 16, first frost Oct 21, zone 5b. whenisthelastfrost.com
Crop
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Start indoors: Jan 22 to Feb 5Transplant outside: Mar 19 to Apr 2
Start indoors: Feb 5 to Feb 19Transplant outside: Apr 30 to May 14
Start indoors: Feb 5 to Feb 19Transplant outside: Apr 30 to May 14
Start indoors: Feb 19 to Mar 5Transplant outside: Apr 23 to May 7
Start indoors: Feb 19 to Mar 5Transplant outside: Mar 26 to Apr 9Sow outdoors: Mar 19 to Apr 23Plant for fall: Aug 26 to Sep 23
Start indoors: Feb 19 to Mar 5Transplant outside: Mar 19 to Apr 2Sow outdoors: Mar 19 to Apr 2Plant for fall: Aug 12 to Sep 2
Start indoors: Feb 19 to Mar 5Transplant outside: Apr 2 to Apr 16Plant for fall: Jul 15 to Aug 5
Start indoors: Feb 19 to Mar 5Transplant outside: Mar 26 to Apr 9Plant for fall: Jul 15 to Aug 5
Start indoors: Feb 19 to Mar 5Transplant outside: Apr 2 to Apr 16Plant for fall: Jul 15 to Aug 5
Start indoors: Mar 5 to Mar 19Transplant outside: May 7 to May 21Sow outdoors: May 7 to May 21
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 23 to May 7
Sow outdoors: Mar 5 to Mar 26Plant for fall: Jul 29 to Aug 19
Sow outdoors: Mar 5 to Mar 26Plant for fall: Aug 26 to Sep 16
Sow outdoors: Mar 12 to Apr 23Plant for fall: Sep 9 to Sep 30
Start indoors: Mar 19 to Mar 26Transplant outside: Apr 30 to May 7Sow outdoors: Apr 23 to May 7Plant for fall: Aug 5 to Aug 19
Start indoors: Mar 19 to Mar 26Sow outdoors: Apr 23 to May 7Plant for fall: Aug 12 to Aug 26
Start indoors: Mar 19 to Mar 26Sow outdoors: Apr 23 to May 7
Start indoors: Mar 19 to Mar 26Transplant outside: Apr 30 to May 14
Sow outdoors: Mar 26 to Apr 23Plant for fall: Jul 29 to Aug 12
Sow outdoors: Mar 26 to Apr 23Plant for fall: Aug 12 to Aug 26
Sow outdoors: Mar 26 to Apr 16
Sow outdoors: Apr 2 to Apr 30Plant for fall: Aug 12 to Aug 26
Sow outdoors: Apr 2 to Apr 23Plant for fall: Aug 26 to Sep 16
Sow outdoors: Apr 23 to May 14Plant for fall: Aug 5 to Aug 19
Sow outdoors: Apr 23 to May 7
Transplant outside: Apr 30 to May 21
Plant for fall: Oct 7 to Nov 11
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Decatur, IA
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Jan 22 – Feb 5 | Mar 19 – Apr 2 | — | — |
| Peppers | Feb 5 – Feb 19 | Apr 30 – May 14 | — | — |
| Eggplant | Feb 5 – Feb 19 | Apr 30 – May 14 | — | — |
| Tomatoes | Feb 19 – Mar 5 | Apr 23 – May 7 | — | — |
| Lettuce | Feb 19 – Mar 5 | Mar 26 – Apr 9 | Mar 19 – Apr 23 | Aug 26 – Sep 23 |
| Kale | Feb 19 – Mar 5 | Mar 19 – Apr 2 | Mar 19 – Apr 2 | Aug 12 – Sep 2 |
| Broccoli | Feb 19 – Mar 5 | Apr 2 – Apr 16 | — | Jul 15 – Aug 5 |
| Cabbage | Feb 19 – Mar 5 | Mar 26 – Apr 9 | — | Jul 15 – Aug 5 |
| Cauliflower | Feb 19 – Mar 5 | Apr 2 – Apr 16 | — | Jul 15 – Aug 5 |
| Okra | Mar 5 – Mar 19 | May 7 – May 21 | May 7 – May 21 | — |
| Basil | Mar 5 – Mar 19 | Apr 23 – May 7 | — | — |
| Peas | — | — | Mar 5 – Mar 26 | Jul 29 – Aug 19 |
| Spinach | — | — | Mar 5 – Mar 26 | Aug 26 – Sep 16 |
| Radishes | — | — | Mar 12 – Apr 23 | Sep 9 – Sep 30 |
| Cucumbers | Mar 19 – Mar 26 | Apr 30 – May 7 | Apr 23 – May 7 | Aug 5 – Aug 19 |
| Zucchini & Summer Squash | Mar 19 – Mar 26 | — | Apr 23 – May 7 | Aug 12 – Aug 26 |
| Winter Squash & Pumpkins | Mar 19 – Mar 26 | — | Apr 23 – May 7 | — |
| Melons & Watermelon | Mar 19 – Mar 26 | Apr 30 – May 14 | — | — |
| Carrots | — | — | Mar 26 – Apr 23 | Jul 29 – Aug 12 |
| Beets | — | — | Mar 26 – Apr 23 | Aug 12 – Aug 26 |
| Potatoes | — | — | Mar 26 – Apr 16 | — |
| Swiss Chard | — | — | Apr 2 – Apr 30 | Aug 12 – Aug 26 |
| Cilantro | — | — | Apr 2 – Apr 23 | Aug 26 – Sep 16 |
| Green Beans | — | — | Apr 23 – May 14 | Aug 5 – Aug 19 |
| Sweet Corn | — | — | Apr 23 – May 7 | — |
| Sweet Potatoes | — | Apr 30 – May 21 | — | — |
| Garlic | — | — | — | Oct 7 – Nov 11 |
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 Lamoni Muni Ap, IA weather station, 14 km away (elevation 1,132 ft (345 m)).
Frost dates near Decatur
- Leon Apr 30 · Oct 8
- Davis City Apr 16 · Oct 21
- Grand River Apr 23 · Oct 17
- Van Wert Apr 29 · Oct 9
- Lamoni Apr 17 · Oct 21
- Weldon Apr 29 · Oct 9
- Garden Grove Apr 30 · Oct 8
- Kellerton Apr 16 · Oct 20
- Ellston Apr 23 · Oct 17
- Humeston Apr 30 · Oct 8
Frequently asked questions
When is the last frost in Decatur, IA?
The median last spring frost in Decatur, IA is April 16. There is still about a 10% chance of frost after May 2, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Decatur, IA?
The median first fall frost is October 21, with about a 10% chance of frost before October 6.
How long is the growing season in Decatur, IA?
About 188 days between the median last spring frost and first fall frost.
What planting zone is Decatur, IA?
Decatur, IA is in USDA hardiness zone 5b.