Ionia, IA frost dates
Last spring frostMay 2median date
First fall frostOct 5median date
Growing season156 daysfrost-free
Hardiness zone5aZone 5a
How Ionia compares
- In 8 years out of 10, the last spring frost in Ionia falls between April 17 and May 14, a 27-day window. The first fall frost falls between September 23 and October 18.
- The median last frost is 4 days later than the Iowa median of Apr 28.
- Its 156-day growing season is longer than 15% 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 158 nights a year at or below 32°F.
- Compared with Waterloo, IA, 63 km away, the last frost here is 5 days later than there and the growing season is 10 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 17 |
| 50% (median) | May 2 |
| 10% (safe for tender plants) | May 14 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 23 |
| 50% (median) | October 5 |
| 90% (late) | October 18 |
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 Ionia, IA
Ionia, IA frost dates — last frost May 2, first frost Oct 5, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Feb 7 to Feb 21Transplant outside: Apr 4 to Apr 18
Start indoors: Feb 21 to Mar 7Transplant outside: May 16 to May 30
Start indoors: Feb 21 to Mar 7Transplant outside: May 16 to May 30
Start indoors: Mar 7 to Mar 21Transplant outside: May 9 to May 23
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 11 to Apr 25Sow outdoors: Apr 4 to May 9Plant for fall: Aug 10 to Sep 7
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 4 to Apr 18Sow outdoors: Apr 4 to Apr 18Plant for fall: Jul 27 to Aug 17
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 18 to May 2Plant for fall: Jun 29 to Jul 20
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 11 to Apr 25Plant for fall: Jun 29 to Jul 20
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 18 to May 2Plant for fall: Jun 29 to Jul 20
Start indoors: Mar 21 to Apr 4Transplant outside: May 23 to Jun 6Sow outdoors: May 23 to Jun 6
Start indoors: Mar 21 to Apr 4Transplant outside: May 9 to May 23
Sow outdoors: Mar 21 to Apr 11Plant for fall: Jul 13 to Aug 3
Sow outdoors: Mar 21 to Apr 11Plant for fall: Aug 10 to Aug 31
Sow outdoors: Mar 28 to May 9Plant for fall: Aug 24 to Sep 14
Start indoors: Apr 4 to Apr 11Transplant outside: May 16 to May 23Sow outdoors: May 9 to May 23Plant for fall: Jul 20 to Aug 3
Start indoors: Apr 4 to Apr 11Sow outdoors: May 9 to May 23Plant for fall: Jul 27 to Aug 10
Start indoors: Apr 4 to Apr 11Sow outdoors: May 9 to May 23
Start indoors: Apr 4 to Apr 11Transplant outside: May 16 to May 30
Sow outdoors: Apr 11 to May 9Plant for fall: Jul 13 to Jul 27
Sow outdoors: Apr 11 to May 9Plant for fall: Jul 27 to Aug 10
Sow outdoors: Apr 11 to May 2
Sow outdoors: Apr 18 to May 16Plant for fall: Jul 27 to Aug 10
Sow outdoors: Apr 18 to May 9Plant for fall: Aug 10 to Aug 31
Sow outdoors: May 9 to May 30Plant for fall: Jul 20 to Aug 3
Sow outdoors: May 9 to May 23
Transplant outside: May 16 to Jun 6
Plant for fall: Sep 21 to Oct 26
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Ionia, IA
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 7 – Feb 21 | Apr 4 – Apr 18 | — | — |
| Peppers | Feb 21 – Mar 7 | May 16 – May 30 | — | — |
| Eggplant | Feb 21 – Mar 7 | May 16 – May 30 | — | — |
| Tomatoes | Mar 7 – Mar 21 | May 9 – May 23 | — | — |
| Lettuce | Mar 7 – Mar 21 | Apr 11 – Apr 25 | Apr 4 – May 9 | Aug 10 – Sep 7 |
| Kale | Mar 7 – Mar 21 | Apr 4 – Apr 18 | Apr 4 – Apr 18 | Jul 27 – Aug 17 |
| Broccoli | Mar 7 – Mar 21 | Apr 18 – May 2 | — | Jun 29 – Jul 20 |
| Cabbage | Mar 7 – Mar 21 | Apr 11 – Apr 25 | — | Jun 29 – Jul 20 |
| Cauliflower | Mar 7 – Mar 21 | Apr 18 – May 2 | — | Jun 29 – Jul 20 |
| Okra | Mar 21 – Apr 4 | May 23 – Jun 6 | May 23 – Jun 6 | — |
| Basil | Mar 21 – Apr 4 | May 9 – May 23 | — | — |
| Peas | — | — | Mar 21 – Apr 11 | Jul 13 – Aug 3 |
| Spinach | — | — | Mar 21 – Apr 11 | Aug 10 – Aug 31 |
| Radishes | — | — | Mar 28 – May 9 | Aug 24 – Sep 14 |
| Cucumbers | Apr 4 – Apr 11 | May 16 – May 23 | May 9 – May 23 | Jul 20 – Aug 3 |
| Zucchini & Summer Squash | Apr 4 – Apr 11 | — | May 9 – May 23 | Jul 27 – Aug 10 |
| Winter Squash & Pumpkins | Apr 4 – Apr 11 | — | May 9 – May 23 | — |
| Melons & Watermelon | Apr 4 – Apr 11 | May 16 – May 30 | — | — |
| Carrots | — | — | Apr 11 – May 9 | Jul 13 – Jul 27 |
| Beets | — | — | Apr 11 – May 9 | Jul 27 – Aug 10 |
| Potatoes | — | — | Apr 11 – May 2 | — |
| Swiss Chard | — | — | Apr 18 – May 16 | Jul 27 – Aug 10 |
| Cilantro | — | — | Apr 18 – May 9 | Aug 10 – Aug 31 |
| Green Beans | — | — | May 9 – May 30 | Jul 20 – Aug 3 |
| Sweet Corn | — | — | May 9 – May 23 | — |
| Sweet Potatoes | — | May 16 – Jun 6 | — | — |
| Garlic | — | — | — | Sep 21 – Oct 26 |
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 New Hampton, IA weather station, 14 km away (elevation 1,148 ft (350 m)).
Frost dates near Ionia
- Nashua Apr 30 · Oct 6
- North Washington May 2 · Oct 5
- Alta Vista May 2 · Oct 5
- New Hampton May 2 · Oct 5
- Colwell Apr 30 · Oct 6
- Charles City Apr 30 · Oct 6
- Plainfield Apr 29 · Oct 9
- Floyd Apr 30 · Oct 6
- Frederika Apr 29 · Oct 9
- Fredericksburg May 2 · Oct 5
Frequently asked questions
When is the last frost in Ionia, IA?
The median last spring frost in Ionia, IA is May 2. 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 Ionia, IA?
The median first fall frost is October 5, with about a 10% chance of frost before September 23.
How long is the growing season in Ionia, IA?
About 156 days between the median last spring frost and first fall frost.
What planting zone is Ionia, IA?
Ionia, IA is in USDA hardiness zone 5a.