Mount Union, IA frost dates
Last spring frostApr 30median date
First fall frostOct 10median date
Growing season163 daysfrost-free
Hardiness zone5bZone 5b
How Mount Union compares
- In 8 years out of 10, the last spring frost in Mount Union falls between April 13 and May 14, a 31-day window. The first fall frost falls between September 24 and October 23.
- The median last frost is 2 days later than the Iowa median of Apr 28.
- Its 163-day growing season is longer than 35% of the 934 Iowa places with a regular frost season (state median 165 days).
- The last frost is typical for zone 5b, where the median is May 1.
- The weather station records an average of 130 nights a year at or below 32°F.
- Compared with Iowa City, IA, 68 km away, the last frost here is 9 days later than there and the growing season is 17 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 13 |
| 50% (median) | April 30 |
| 10% (safe for tender plants) | May 14 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 24 |
| 50% (median) | October 10 |
| 90% (late) | October 23 |
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 Mount Union, IA
Mount Union, IA frost dates — last frost Apr 30, first frost Oct 10, zone 5b. 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 15 to Sep 12
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 2 to Apr 16Sow outdoors: Apr 2 to Apr 16Plant for fall: Aug 1 to Aug 22
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 16 to Apr 30Plant for fall: Jul 4 to Jul 25
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 9 to Apr 23Plant for fall: Jul 4 to Jul 25
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 16 to Apr 30Plant for fall: Jul 4 to Jul 25
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 18 to Aug 8
Sow outdoors: Mar 19 to Apr 9Plant for fall: Aug 15 to Sep 5
Sow outdoors: Mar 26 to May 7Plant for fall: Aug 29 to Sep 19
Start indoors: Apr 2 to Apr 9Transplant outside: May 14 to May 21Sow outdoors: May 7 to May 21Plant for fall: Jul 25 to Aug 8
Start indoors: Apr 2 to Apr 9Sow outdoors: May 7 to May 21Plant for fall: Aug 1 to Aug 15
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 18 to Aug 1
Sow outdoors: Apr 9 to May 7Plant for fall: Aug 1 to Aug 15
Sow outdoors: Apr 9 to Apr 30
Sow outdoors: Apr 16 to May 14Plant for fall: Aug 1 to Aug 15
Sow outdoors: Apr 16 to May 7Plant for fall: Aug 15 to Sep 5
Sow outdoors: May 7 to May 28Plant for fall: Jul 25 to Aug 8
Sow outdoors: May 7 to May 21
Transplant outside: May 14 to Jun 4
Plant for fall: Sep 26 to Oct 31
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Mount Union, 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 15 – Sep 12 |
| Kale | Mar 5 – Mar 19 | Apr 2 – Apr 16 | Apr 2 – Apr 16 | Aug 1 – Aug 22 |
| Broccoli | Mar 5 – Mar 19 | Apr 16 – Apr 30 | — | Jul 4 – Jul 25 |
| Cabbage | Mar 5 – Mar 19 | Apr 9 – Apr 23 | — | Jul 4 – Jul 25 |
| Cauliflower | Mar 5 – Mar 19 | Apr 16 – Apr 30 | — | Jul 4 – Jul 25 |
| 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 18 – Aug 8 |
| Spinach | — | — | Mar 19 – Apr 9 | Aug 15 – Sep 5 |
| Radishes | — | — | Mar 26 – May 7 | Aug 29 – Sep 19 |
| Cucumbers | Apr 2 – Apr 9 | May 14 – May 21 | May 7 – May 21 | Jul 25 – Aug 8 |
| Zucchini & Summer Squash | Apr 2 – Apr 9 | — | May 7 – May 21 | Aug 1 – Aug 15 |
| 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 18 – Aug 1 |
| Beets | — | — | Apr 9 – May 7 | Aug 1 – Aug 15 |
| Potatoes | — | — | Apr 9 – Apr 30 | — |
| Swiss Chard | — | — | Apr 16 – May 14 | Aug 1 – Aug 15 |
| Cilantro | — | — | Apr 16 – May 7 | Aug 15 – Sep 5 |
| Green Beans | — | — | May 7 – May 28 | Jul 25 – Aug 8 |
| Sweet Corn | — | — | May 7 – May 21 | — |
| Sweet Potatoes | — | May 14 – Jun 4 | — | — |
| Garlic | — | — | — | Sep 26 – Oct 31 |
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 Mt Pleasant 1 Ssw, IA weather station, 16 km away (elevation 732 ft (223 m)).
Frost dates near Mount Union
- Winfield Apr 26 · Oct 10
- Yarmouth Apr 30 · Oct 10
- Swedesburg Apr 30 · Oct 10
- New London Apr 30 · Oct 10
- Mount Pleasant Apr 30 · Oct 10
- Morning Sun Apr 14 · Oct 24
- Olds Apr 30 · Oct 10
- Crawfordsville Apr 28 · Oct 11
- Sperry Apr 8 · Oct 29
- Danville Apr 15 · Oct 20
Frequently asked questions
When is the last frost in Mount Union, IA?
The median last spring frost in Mount Union, IA is April 30. 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 Mount Union, IA?
The median first fall frost is October 10, with about a 10% chance of frost before September 24.
How long is the growing season in Mount Union, IA?
About 163 days between the median last spring frost and first fall frost.
What planting zone is Mount Union, IA?
Mount Union, IA is in USDA hardiness zone 5b.