Merrill, IA frost dates
Last spring frostApr 30median date
First fall frostOct 4median date
Growing season157 daysfrost-free
Hardiness zone5aZone 5a
How Merrill compares
- In 8 years out of 10, the last spring frost in Merrill falls between April 17 and May 12, a 25-day window. The first fall frost falls between September 21 and October 19.
- The median last frost is 2 days later than the Iowa median of Apr 28.
- Its 157-day growing season is longer than 20% 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 160 nights a year at or below 32°F.
- Compared with Sioux City, IA, 28 km away, the last frost here is 1 day later than there and the growing season is 4 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 17 |
| 50% (median) | April 30 |
| 10% (safe for tender plants) | May 12 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 21 |
| 50% (median) | October 4 |
| 90% (late) | October 19 |
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 Merrill, IA
Merrill, IA frost dates — last frost Apr 30, first frost Oct 4, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Feb 5 to Feb 19Transplant outside: Apr 2 to Apr 16
Start indoors: Feb 19 to Mar 5Transplant outside: May 14 to May 28
Start indoors: Feb 19 to Mar 5Transplant outside: May 14 to May 28
Start indoors: Mar 5 to Mar 19Transplant outside: May 7 to May 21
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 9 to Apr 23Sow outdoors: Apr 2 to May 7Plant for fall: Aug 9 to Sep 6
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 2 to Apr 16Sow outdoors: Apr 2 to Apr 16Plant for fall: Jul 26 to Aug 16
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 16 to Apr 30Plant for fall: Jun 28 to Jul 19
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 9 to Apr 23Plant for fall: Jun 28 to Jul 19
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 16 to Apr 30Plant for fall: Jun 28 to Jul 19
Start indoors: Mar 19 to Apr 2Transplant outside: May 21 to Jun 4Sow outdoors: May 21 to Jun 4
Start indoors: Mar 19 to Apr 2Transplant outside: May 7 to May 21
Sow outdoors: Mar 19 to Apr 9Plant for fall: Jul 12 to Aug 2
Sow outdoors: Mar 19 to Apr 9Plant for fall: Aug 9 to Aug 30
Sow outdoors: Mar 26 to May 7Plant for fall: Aug 23 to Sep 13
Start indoors: Apr 2 to Apr 9Transplant outside: May 14 to May 21Sow outdoors: May 7 to May 21Plant for fall: Jul 19 to Aug 2
Start indoors: Apr 2 to Apr 9Sow outdoors: May 7 to May 21Plant for fall: Jul 26 to Aug 9
Start indoors: Apr 2 to Apr 9Sow outdoors: May 7 to May 21
Start indoors: Apr 2 to Apr 9Transplant outside: May 14 to May 28
Sow outdoors: Apr 9 to May 7Plant for fall: Jul 12 to Jul 26
Sow outdoors: Apr 9 to May 7Plant for fall: Jul 26 to Aug 9
Sow outdoors: Apr 9 to Apr 30
Sow outdoors: Apr 16 to May 14Plant for fall: Jul 26 to Aug 9
Sow outdoors: Apr 16 to May 7Plant for fall: Aug 9 to Aug 30
Sow outdoors: May 7 to May 28Plant for fall: Jul 19 to Aug 2
Sow outdoors: May 7 to May 21
Transplant outside: May 14 to Jun 4
Plant for fall: Sep 20 to Oct 25
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Merrill, IA
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 5 – Feb 19 | Apr 2 – Apr 16 | — | — |
| Peppers | Feb 19 – Mar 5 | May 14 – May 28 | — | — |
| Eggplant | Feb 19 – Mar 5 | May 14 – May 28 | — | — |
| Tomatoes | Mar 5 – Mar 19 | May 7 – May 21 | — | — |
| Lettuce | Mar 5 – Mar 19 | Apr 9 – Apr 23 | Apr 2 – May 7 | Aug 9 – Sep 6 |
| Kale | Mar 5 – Mar 19 | Apr 2 – Apr 16 | Apr 2 – Apr 16 | Jul 26 – Aug 16 |
| Broccoli | Mar 5 – Mar 19 | Apr 16 – Apr 30 | — | Jun 28 – Jul 19 |
| Cabbage | Mar 5 – Mar 19 | Apr 9 – Apr 23 | — | Jun 28 – Jul 19 |
| Cauliflower | Mar 5 – Mar 19 | Apr 16 – Apr 30 | — | Jun 28 – Jul 19 |
| Okra | Mar 19 – Apr 2 | May 21 – Jun 4 | May 21 – Jun 4 | — |
| Basil | Mar 19 – Apr 2 | May 7 – May 21 | — | — |
| Peas | — | — | Mar 19 – Apr 9 | Jul 12 – Aug 2 |
| Spinach | — | — | Mar 19 – Apr 9 | Aug 9 – Aug 30 |
| Radishes | — | — | Mar 26 – May 7 | Aug 23 – Sep 13 |
| Cucumbers | Apr 2 – Apr 9 | May 14 – May 21 | May 7 – May 21 | Jul 19 – Aug 2 |
| Zucchini & Summer Squash | Apr 2 – Apr 9 | — | May 7 – May 21 | Jul 26 – Aug 9 |
| Winter Squash & Pumpkins | Apr 2 – Apr 9 | — | May 7 – May 21 | — |
| Melons & Watermelon | Apr 2 – Apr 9 | May 14 – May 28 | — | — |
| Carrots | — | — | Apr 9 – May 7 | Jul 12 – Jul 26 |
| Beets | — | — | Apr 9 – May 7 | Jul 26 – Aug 9 |
| Potatoes | — | — | Apr 9 – Apr 30 | — |
| Swiss Chard | — | — | Apr 16 – May 14 | Jul 26 – Aug 9 |
| Cilantro | — | — | Apr 16 – May 7 | Aug 9 – Aug 30 |
| Green Beans | — | — | May 7 – May 28 | Jul 19 – Aug 2 |
| Sweet Corn | — | — | May 7 – May 21 | — |
| Sweet Potatoes | — | May 14 – Jun 4 | — | — |
| Garlic | — | — | — | Sep 20 – Oct 25 |
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 Le Mars, IA weather station, 11 km away (elevation 1,194 ft (364 m)).
Frost dates near Merrill
- Le Mars Apr 30 · Oct 4
- Brunsville Apr 30 · Oct 4
- Hinton Apr 30 · Oct 4
- Oyens Apr 30 · Oct 4
- Westfield Apr 30 · Oct 4
- Lawton Apr 29 · Oct 7
- Kingsley Apr 30 · Oct 4
- Remsen Apr 30 · Oct 4
- Akron May 1 · Oct 4
- Sioux City Apr 29 · Oct 7
Frequently asked questions
When is the last frost in Merrill, IA?
The median last spring frost in Merrill, IA is April 30. 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 Merrill, IA?
The median first fall frost is October 4, with about a 10% chance of frost before September 21.
How long is the growing season in Merrill, IA?
About 157 days between the median last spring frost and first fall frost.
What planting zone is Merrill, IA?
Merrill, IA is in USDA hardiness zone 5a.