Irons, MI frost dates
Last spring frostMay 28median date
First fall frostSep 25median date
Growing season120 daysfrost-free
Hardiness zone5bZone 5b
How Irons compares
- In 8 years out of 10, the last spring frost in Irons falls between May 13 and June 13, a 31-day window. The first fall frost falls between September 8 and October 10.
- The median last frost is 23 days later than the Michigan median of May 5.
- Its 120-day growing season is longer than 3% of the 878 Michigan places with a regular frost season (state median 162 days).
- The last frost is 27 days later than the zone 5b median of May 1. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5b chart.
- The weather station records an average of 171 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 13 |
| 50% (median) | May 28 |
| 10% (safe for tender plants) | June 13 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 8 |
| 50% (median) | September 25 |
| 90% (late) | October 10 |
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 Irons, MI
Irons, MI frost dates — last frost May 28, first frost Sep 25, zone 5b. whenisthelastfrost.com
Crop
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Start indoors: Mar 5 to Mar 19Transplant outside: Apr 30 to May 14
Start indoors: Mar 19 to Apr 2Transplant outside: Jun 11 to Jun 25
Start indoors: Mar 19 to Apr 2Transplant outside: Jun 11 to Jun 25
Start indoors: Apr 2 to Apr 16Transplant outside: Jun 4 to Jun 18
Start indoors: Apr 2 to Apr 16Transplant outside: May 7 to May 21Sow outdoors: Apr 30 to Jun 4Plant for fall: Jul 31 to Aug 28
Start indoors: Apr 2 to Apr 16Transplant outside: Apr 30 to May 14Sow outdoors: Apr 30 to May 14Plant for fall: Jul 17 to Aug 7
Start indoors: Apr 2 to Apr 16Transplant outside: May 14 to May 28Plant for fall: Jun 19 to Jul 10
Start indoors: Apr 2 to Apr 16Transplant outside: May 7 to May 21Plant for fall: Jun 19 to Jul 10
Start indoors: Apr 2 to Apr 16Transplant outside: May 14 to May 28Plant for fall: Jun 19 to Jul 10
Start indoors: Apr 16 to Apr 30Transplant outside: Jun 18 to Jul 2Sow outdoors: Jun 18 to Jul 2
Start indoors: Apr 16 to Apr 30Transplant outside: Jun 4 to Jun 18
Sow outdoors: Apr 16 to May 7Plant for fall: Jul 3 to Jul 24
Sow outdoors: Apr 16 to May 7Plant for fall: Jul 31 to Aug 21
Sow outdoors: Apr 23 to Jun 4Plant for fall: Aug 14 to Sep 4
Start indoors: Apr 30 to May 7Transplant outside: Jun 11 to Jun 18Sow outdoors: Jun 4 to Jun 18Plant for fall: Jul 10 to Jul 24
Start indoors: Apr 30 to May 7Sow outdoors: Jun 4 to Jun 18Plant for fall: Jul 17 to Jul 31
Start indoors: Apr 30 to May 7Sow outdoors: Jun 4 to Jun 18
Start indoors: Apr 30 to May 7Transplant outside: Jun 11 to Jun 25
Sow outdoors: May 7 to Jun 4Plant for fall: Jul 3 to Jul 17
Sow outdoors: May 7 to Jun 4Plant for fall: Jul 17 to Jul 31
Sow outdoors: May 7 to May 28
Sow outdoors: May 14 to Jun 11Plant for fall: Jul 17 to Jul 31
Sow outdoors: May 14 to Jun 4Plant for fall: Jul 31 to Aug 21
Sow outdoors: Jun 4 to Jun 25Plant for fall: Jul 10 to Jul 24
Sow outdoors: Jun 4 to Jun 18
Transplant outside: Jun 11 to Jul 2
Plant for fall: Sep 11 to Oct 16
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Irons, MI
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Mar 5 – Mar 19 | Apr 30 – May 14 | — | — |
| Peppers | Mar 19 – Apr 2 | Jun 11 – Jun 25 | — | — |
| Eggplant | Mar 19 – Apr 2 | Jun 11 – Jun 25 | — | — |
| Tomatoes | Apr 2 – Apr 16 | Jun 4 – Jun 18 | — | — |
| Lettuce | Apr 2 – Apr 16 | May 7 – May 21 | Apr 30 – Jun 4 | Jul 31 – Aug 28 |
| Kale | Apr 2 – Apr 16 | Apr 30 – May 14 | Apr 30 – May 14 | Jul 17 – Aug 7 |
| Broccoli | Apr 2 – Apr 16 | May 14 – May 28 | — | Jun 19 – Jul 10 |
| Cabbage | Apr 2 – Apr 16 | May 7 – May 21 | — | Jun 19 – Jul 10 |
| Cauliflower | Apr 2 – Apr 16 | May 14 – May 28 | — | Jun 19 – Jul 10 |
| Okra | Apr 16 – Apr 30 | Jun 18 – Jul 2 | Jun 18 – Jul 2 | — |
| Basil | Apr 16 – Apr 30 | Jun 4 – Jun 18 | — | — |
| Peas | — | — | Apr 16 – May 7 | Jul 3 – Jul 24 |
| Spinach | — | — | Apr 16 – May 7 | Jul 31 – Aug 21 |
| Radishes | — | — | Apr 23 – Jun 4 | Aug 14 – Sep 4 |
| Cucumbers | Apr 30 – May 7 | Jun 11 – Jun 18 | Jun 4 – Jun 18 | Jul 10 – Jul 24 |
| Zucchini & Summer Squash | Apr 30 – May 7 | — | Jun 4 – Jun 18 | Jul 17 – Jul 31 |
| Winter Squash & Pumpkins | Apr 30 – May 7 | — | Jun 4 – Jun 18 | — |
| Melons & Watermelon | Apr 30 – May 7 | Jun 11 – Jun 25 | — | — |
| Carrots | — | — | May 7 – Jun 4 | Jul 3 – Jul 17 |
| Beets | — | — | May 7 – Jun 4 | Jul 17 – Jul 31 |
| Potatoes | — | — | May 7 – May 28 | — |
| Swiss Chard | — | — | May 14 – Jun 11 | Jul 17 – Jul 31 |
| Cilantro | — | — | May 14 – Jun 4 | Jul 31 – Aug 21 |
| Green Beans | — | — | Jun 4 – Jun 25 | Jul 10 – Jul 24 |
| Sweet Corn | — | — | Jun 4 – Jun 18 | — |
| Sweet Potatoes | — | Jun 11 – Jul 2 | — | — |
| Garlic | — | — | — | Sep 11 – Oct 16 |
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 Wellston 1n, MI weather station, 15 km away (elevation 774 ft (236 m)).
Frost dates near Irons
- Wellston May 28 · Sep 25
- Branch May 17 · Oct 7
- Luther May 15 · Oct 1
- Walhalla May 17 · Oct 7
- Brethren May 28 · Sep 25
- Fountain May 17 · Oct 7
- Baldwin May 17 · Oct 1
- Free Soil May 14 · Oct 12
- Custer May 17 · Oct 7
- Idlewild May 13 · Oct 2
Frequently asked questions
When is the last frost in Irons, MI?
The median last spring frost in Irons, MI is May 28. There is still about a 10% chance of frost after June 13, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Irons, MI?
The median first fall frost is September 25, with about a 10% chance of frost before September 8.
How long is the growing season in Irons, MI?
About 120 days between the median last spring frost and first fall frost.
What planting zone is Irons, MI?
Irons, MI is in USDA hardiness zone 5b.