Union, MI frost dates
Last spring frostApr 30median date
First fall frostOct 17median date
Growing season170 daysfrost-free
Hardiness zone6aZone 6a
How Union compares
- In 8 years out of 10, the last spring frost in Union falls between April 16 and May 15, a 29-day window. The first fall frost falls between October 1 and November 1.
- The median last frost is 5 days earlier than the Michigan median of May 5.
- Its 170-day growing season is longer than 73% of the 878 Michigan places with a regular frost season (state median 162 days).
- The last frost is typical for zone 6a, where the median is Apr 29.
- The weather station records an average of 145 nights a year at or below 32°F.
- Compared with Elkhart, IN, 15 km away, the last frost here is 4 days later than there and the growing season is 8 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 16 |
| 50% (median) | April 30 |
| 10% (safe for tender plants) | May 15 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 1 |
| 50% (median) | October 17 |
| 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 Union, MI
Union, MI frost dates — last frost Apr 30, first frost Oct 17, zone 6a. 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 22 to Sep 19
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 2 to Apr 16Sow outdoors: Apr 2 to Apr 16Plant for fall: Aug 8 to Aug 29
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 16 to Apr 30Plant for fall: Jul 11 to Aug 1
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 9 to Apr 23Plant for fall: Jul 11 to Aug 1
Start indoors: Mar 5 to Mar 19Transplant outside: Apr 16 to Apr 30Plant for fall: Jul 11 to Aug 1
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 25 to Aug 15
Sow outdoors: Mar 19 to Apr 9Plant for fall: Aug 22 to Sep 12
Sow outdoors: Mar 26 to May 7Plant for fall: Sep 5 to Sep 26
Start indoors: Apr 2 to Apr 9Transplant outside: May 14 to May 21Sow 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 21Plant for fall: Aug 8 to Aug 22
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 25 to Aug 8
Sow outdoors: Apr 9 to May 7Plant for fall: Aug 8 to Aug 22
Sow outdoors: Apr 9 to Apr 30
Sow outdoors: Apr 16 to May 14Plant for fall: Aug 8 to Aug 22
Sow outdoors: Apr 16 to May 7Plant for fall: Aug 22 to Sep 12
Sow outdoors: May 7 to May 28Plant for fall: Aug 1 to Aug 15
Sow outdoors: May 7 to May 21
Transplant outside: May 14 to Jun 4
Plant for fall: Oct 3 to Nov 7
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Union, MI
| 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 22 – Sep 19 |
| Kale | Mar 5 – Mar 19 | Apr 2 – Apr 16 | Apr 2 – Apr 16 | Aug 8 – Aug 29 |
| Broccoli | Mar 5 – Mar 19 | Apr 16 – Apr 30 | — | Jul 11 – Aug 1 |
| Cabbage | Mar 5 – Mar 19 | Apr 9 – Apr 23 | — | Jul 11 – Aug 1 |
| Cauliflower | Mar 5 – Mar 19 | Apr 16 – Apr 30 | — | Jul 11 – Aug 1 |
| 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 25 – Aug 15 |
| Spinach | — | — | Mar 19 – Apr 9 | Aug 22 – Sep 12 |
| Radishes | — | — | Mar 26 – May 7 | Sep 5 – Sep 26 |
| Cucumbers | Apr 2 – Apr 9 | May 14 – May 21 | May 7 – May 21 | Aug 1 – Aug 15 |
| Zucchini & Summer Squash | Apr 2 – Apr 9 | — | May 7 – May 21 | Aug 8 – Aug 22 |
| 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 25 – Aug 8 |
| Beets | — | — | Apr 9 – May 7 | Aug 8 – Aug 22 |
| Potatoes | — | — | Apr 9 – Apr 30 | — |
| Swiss Chard | — | — | Apr 16 – May 14 | Aug 8 – Aug 22 |
| Cilantro | — | — | Apr 16 – May 7 | Aug 22 – Sep 12 |
| Green Beans | — | — | May 7 – May 28 | Aug 1 – Aug 15 |
| Sweet Corn | — | — | May 7 – May 21 | — |
| Sweet Potatoes | — | May 14 – Jun 4 | — | — |
| Garlic | — | — | — | Oct 3 – Nov 7 |
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 Three Rivers, MI weather station, 24 km away (elevation 810 ft (247 m)).
Frost dates near Union
- Vandalia Apr 30 · Oct 17
- Edwardsburg Apr 27 · Oct 25
- Jones Apr 30 · Oct 17
- White Pigeon Apr 30 · Oct 17
- Cassopolis May 4 · Oct 11
- Constantine Apr 30 · Oct 17
- Three Rivers Apr 30 · Oct 17
- Marcellus Apr 30 · Oct 17
- Dowagiac May 4 · Oct 11
- Niles Apr 27 · Oct 25
Frequently asked questions
When is the last frost in Union, MI?
The median last spring frost in Union, MI is April 30. There is still about a 10% chance of frost after May 15, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Union, MI?
The median first fall frost is October 17, with about a 10% chance of frost before October 1.
How long is the growing season in Union, MI?
About 170 days between the median last spring frost and first fall frost.
What planting zone is Union, MI?
Union, MI is in USDA hardiness zone 6a.