Marengo, IA frost dates
Last spring frostApr 28median date
First fall frostOct 9median date
Growing season164 daysfrost-free
Hardiness zone5aZone 5a
How Marengo compares
- In 8 years out of 10, the last spring frost in Marengo falls between April 14 and May 12, a 28-day window. The first fall frost falls between September 24 and October 21.
- The median last frost is the same as the Iowa median of Apr 28.
- Its 164-day growing season is longer than 43% of the 934 Iowa places with a regular frost season (state median 165 days).
- The last frost is 5 days earlier than the zone 5a median of May 3. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5a chart.
- The weather station records an average of 151 nights a year at or below 32°F.
- Compared with Cedar Rapids, IA, 46 km away, the last frost here is the same as there and the growing season is 3 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 14 |
| 50% (median) | April 28 |
| 10% (safe for tender plants) | May 12 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 24 |
| 50% (median) | October 9 |
| 90% (late) | October 21 |
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 Marengo, IA
Marengo, IA frost dates — last frost Apr 28, first frost Oct 9, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Feb 3 to Feb 17Transplant outside: Mar 31 to Apr 14
Start indoors: Feb 17 to Mar 3Transplant outside: May 12 to May 26
Start indoors: Feb 17 to Mar 3Transplant outside: May 12 to May 26
Start indoors: Mar 3 to Mar 17Transplant outside: May 5 to May 19
Start indoors: Mar 3 to Mar 17Transplant outside: Apr 7 to Apr 21Sow outdoors: Mar 31 to May 5Plant for fall: Aug 14 to Sep 11
Start indoors: Mar 3 to Mar 17Transplant outside: Mar 31 to Apr 14Sow outdoors: Mar 31 to Apr 14Plant for fall: Jul 31 to Aug 21
Start indoors: Mar 3 to Mar 17Transplant outside: Apr 14 to Apr 28Plant for fall: Jul 3 to Jul 24
Start indoors: Mar 3 to Mar 17Transplant outside: Apr 7 to Apr 21Plant for fall: Jul 3 to Jul 24
Start indoors: Mar 3 to Mar 17Transplant outside: Apr 14 to Apr 28Plant for fall: Jul 3 to Jul 24
Start indoors: Mar 17 to Mar 31Transplant outside: May 19 to Jun 2Sow outdoors: May 19 to Jun 2
Start indoors: Mar 17 to Mar 31Transplant outside: May 5 to May 19
Sow outdoors: Mar 17 to Apr 7Plant for fall: Jul 17 to Aug 7
Sow outdoors: Mar 17 to Apr 7Plant for fall: Aug 14 to Sep 4
Sow outdoors: Mar 24 to May 5Plant for fall: Aug 28 to Sep 18
Start indoors: Mar 31 to Apr 7Transplant outside: May 12 to May 19Sow outdoors: May 5 to May 19Plant for fall: Jul 24 to Aug 7
Start indoors: Mar 31 to Apr 7Sow outdoors: May 5 to May 19Plant for fall: Jul 31 to Aug 14
Start indoors: Mar 31 to Apr 7Sow outdoors: May 5 to May 19
Start indoors: Mar 31 to Apr 7Transplant outside: May 12 to May 26
Sow outdoors: Apr 7 to May 5Plant for fall: Jul 17 to Jul 31
Sow outdoors: Apr 7 to May 5Plant for fall: Jul 31 to Aug 14
Sow outdoors: Apr 7 to Apr 28
Sow outdoors: Apr 14 to May 12Plant for fall: Jul 31 to Aug 14
Sow outdoors: Apr 14 to May 5Plant for fall: Aug 14 to Sep 4
Sow outdoors: May 5 to May 26Plant for fall: Jul 24 to Aug 7
Sow outdoors: May 5 to May 19
Transplant outside: May 12 to Jun 2
Plant for fall: Sep 25 to Oct 30
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Marengo, IA
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 3 – Feb 17 | Mar 31 – Apr 14 | — | — |
| Peppers | Feb 17 – Mar 3 | May 12 – May 26 | — | — |
| Eggplant | Feb 17 – Mar 3 | May 12 – May 26 | — | — |
| Tomatoes | Mar 3 – Mar 17 | May 5 – May 19 | — | — |
| Lettuce | Mar 3 – Mar 17 | Apr 7 – Apr 21 | Mar 31 – May 5 | Aug 14 – Sep 11 |
| Kale | Mar 3 – Mar 17 | Mar 31 – Apr 14 | Mar 31 – Apr 14 | Jul 31 – Aug 21 |
| Broccoli | Mar 3 – Mar 17 | Apr 14 – Apr 28 | — | Jul 3 – Jul 24 |
| Cabbage | Mar 3 – Mar 17 | Apr 7 – Apr 21 | — | Jul 3 – Jul 24 |
| Cauliflower | Mar 3 – Mar 17 | Apr 14 – Apr 28 | — | Jul 3 – Jul 24 |
| Okra | Mar 17 – Mar 31 | May 19 – Jun 2 | May 19 – Jun 2 | — |
| Basil | Mar 17 – Mar 31 | May 5 – May 19 | — | — |
| Peas | — | — | Mar 17 – Apr 7 | Jul 17 – Aug 7 |
| Spinach | — | — | Mar 17 – Apr 7 | Aug 14 – Sep 4 |
| Radishes | — | — | Mar 24 – May 5 | Aug 28 – Sep 18 |
| Cucumbers | Mar 31 – Apr 7 | May 12 – May 19 | May 5 – May 19 | Jul 24 – Aug 7 |
| Zucchini & Summer Squash | Mar 31 – Apr 7 | — | May 5 – May 19 | Jul 31 – Aug 14 |
| Winter Squash & Pumpkins | Mar 31 – Apr 7 | — | May 5 – May 19 | — |
| Melons & Watermelon | Mar 31 – Apr 7 | May 12 – May 26 | — | — |
| Carrots | — | — | Apr 7 – May 5 | Jul 17 – Jul 31 |
| Beets | — | — | Apr 7 – May 5 | Jul 31 – Aug 14 |
| Potatoes | — | — | Apr 7 – Apr 28 | — |
| Swiss Chard | — | — | Apr 14 – May 12 | Jul 31 – Aug 14 |
| Cilantro | — | — | Apr 14 – May 5 | Aug 14 – Sep 4 |
| Green Beans | — | — | May 5 – May 26 | Jul 24 – Aug 7 |
| Sweet Corn | — | — | May 5 – May 19 | — |
| Sweet Potatoes | — | May 12 – Jun 2 | — | — |
| Garlic | — | — | — | Sep 25 – Oct 30 |
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 Williamsburg 1e, IA weather station, 15 km away (elevation 781 ft (238 m)).
Frost dates near Marengo
- Conroy Apr 28 · Oct 9
- Ladora Apr 28 · Oct 10
- South Amana Apr 28 · Oct 9
- Blairstown Apr 28 · Oct 10
- Middle Amana Apr 28 · Oct 9
- Watkins Apr 27 · Oct 11
- Luzerne Apr 28 · Oct 10
- Amana Apr 27 · Oct 11
- Williamsburg Apr 28 · Oct 9
- Homestead Apr 28 · Oct 9
Frequently asked questions
When is the last frost in Marengo, IA?
The median last spring frost in Marengo, IA is April 28. There is still about a 10% chance of frost after May 12, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Marengo, IA?
The median first fall frost is October 9, with about a 10% chance of frost before September 24.
How long is the growing season in Marengo, IA?
About 164 days between the median last spring frost and first fall frost.
What planting zone is Marengo, IA?
Marengo, IA is in USDA hardiness zone 5a.