Iron River, MI frost dates
Last spring frostJun 4median date
First fall frostSep 10median date
Growing season98 daysfrost-free
Hardiness zone4aZone 4a
How Iron River compares
- In 8 years out of 10, the last spring frost in Iron River falls between May 22 and June 26, a 35-day window. The first fall frost falls between August 21 and September 25.
- The median last frost is 30 days later than the Michigan median of May 5.
- Its 98-day growing season is among the shortest of the 878 Michigan places with a regular frost season.
- The last frost is 23 days later than the zone 4a median of May 12. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 4a chart.
- The weather station records an average of 211 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 22 |
| 50% (median) | June 4 |
| 10% (safe for tender plants) | June 26 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | August 21 |
| 50% (median) | September 10 |
| 90% (late) | September 25 |
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 Iron River, MI
Iron River, MI frost dates — last frost Jun 4, first frost Sep 10, zone 4a. whenisthelastfrost.com
Crop
JFMAMJJASOND
Start indoors: Mar 12 to Mar 26Transplant outside: May 7 to May 21
Start indoors: Mar 26 to Apr 9Transplant outside: Jun 18 to Jul 2
Start indoors: Mar 26 to Apr 9Transplant outside: Jun 18 to Jul 2
Start indoors: Apr 9 to Apr 23Transplant outside: Jun 11 to Jun 25
Start indoors: Apr 9 to Apr 23Transplant outside: May 14 to May 28Sow outdoors: May 7 to Jun 11Plant for fall: Jul 16 to Aug 13
Start indoors: Apr 9 to Apr 23Transplant outside: May 7 to May 21Sow outdoors: May 7 to May 21Plant for fall: Jul 2 to Jul 23
Start indoors: Apr 9 to Apr 23Transplant outside: May 21 to Jun 4
Start indoors: Apr 9 to Apr 23Transplant outside: May 14 to May 28
Start indoors: Apr 9 to Apr 23Transplant outside: May 21 to Jun 4
Start indoors: Apr 23 to May 7Transplant outside: Jun 25 to Jul 9Sow outdoors: Jun 25 to Jul 9
Start indoors: Apr 23 to May 7Transplant outside: Jun 11 to Jun 25
Sow outdoors: Apr 23 to May 14
Sow outdoors: Apr 23 to May 14Plant for fall: Jul 16 to Aug 6
Sow outdoors: Apr 30 to Jun 11Plant for fall: Jul 30 to Aug 20
Start indoors: May 7 to May 14Transplant outside: Jun 18 to Jun 25Sow outdoors: Jun 11 to Jun 25
Start indoors: May 7 to May 14Sow outdoors: Jun 11 to Jun 25
Start indoors: May 7 to May 14Sow outdoors: Jun 11 to Jun 25
Start indoors: May 7 to May 14Transplant outside: Jun 18 to Jul 2
Sow outdoors: May 14 to Jun 11
Sow outdoors: May 14 to Jun 11Plant for fall: Jul 2 to Jul 16
Sow outdoors: May 14 to Jun 4
Sow outdoors: May 21 to Jun 18
Sow outdoors: May 21 to Jun 11Plant for fall: Jul 16 to Aug 6
Sow outdoors: Jun 11 to Jul 2
Sow outdoors: Jun 11 to Jun 25
Transplant outside: Jun 18 to Jul 9
Plant for fall: Aug 27 to Oct 1
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Iron River, MI
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Mar 12 – Mar 26 | May 7 – May 21 | — | — |
| Peppers | Mar 26 – Apr 9 | Jun 18 – Jul 2 | — | — |
| Eggplant | Mar 26 – Apr 9 | Jun 18 – Jul 2 | — | — |
| Tomatoes | Apr 9 – Apr 23 | Jun 11 – Jun 25 | — | — |
| Lettuce | Apr 9 – Apr 23 | May 14 – May 28 | May 7 – Jun 11 | Jul 16 – Aug 13 |
| Kale | Apr 9 – Apr 23 | May 7 – May 21 | May 7 – May 21 | Jul 2 – Jul 23 |
| Broccoli | Apr 9 – Apr 23 | May 21 – Jun 4 | — | — |
| Cabbage | Apr 9 – Apr 23 | May 14 – May 28 | — | — |
| Cauliflower | Apr 9 – Apr 23 | May 21 – Jun 4 | — | — |
| Okra | Apr 23 – May 7 | Jun 25 – Jul 9 | Jun 25 – Jul 9 | — |
| Basil | Apr 23 – May 7 | Jun 11 – Jun 25 | — | — |
| Peas | — | — | Apr 23 – May 14 | — |
| Spinach | — | — | Apr 23 – May 14 | Jul 16 – Aug 6 |
| Radishes | — | — | Apr 30 – Jun 11 | Jul 30 – Aug 20 |
| Cucumbers | May 7 – May 14 | Jun 18 – Jun 25 | Jun 11 – Jun 25 | — |
| Zucchini & Summer Squash | May 7 – May 14 | — | Jun 11 – Jun 25 | — |
| Winter Squash & Pumpkins Warning: Your frost-free season is about 98 days, which is tight for winter squash & pumpkins (100+ days). Choose early varieties and use transplants or row covers. | May 7 – May 14 | — | Jun 11 – Jun 25 | — |
| Melons & Watermelon Warning: Your frost-free season is about 98 days, which is tight for melons & watermelon (85+ days). Choose early varieties and use transplants or row covers. | May 7 – May 14 | Jun 18 – Jul 2 | — | — |
| Carrots | — | — | May 14 – Jun 11 | — |
| Beets | — | — | May 14 – Jun 11 | Jul 2 – Jul 16 |
| Potatoes | — | — | May 14 – Jun 4 | — |
| Swiss Chard | — | — | May 21 – Jun 18 | — |
| Cilantro | — | — | May 21 – Jun 11 | Jul 16 – Aug 6 |
| Green Beans | — | — | Jun 11 – Jul 2 | — |
| Sweet Corn | — | — | Jun 11 – Jun 25 | — |
| Sweet Potatoes Warning: Your frost-free season is about 98 days, which is tight for sweet potatoes (100+ days). Choose early varieties and use transplants or row covers. | — | Jun 18 – Jul 9 | — | — |
| Garlic | — | — | — | Aug 27 – Oct 1 |
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 Stambaugh 2sse, MI weather station, 4 km away (elevation 1,450 ft (442 m)).
Frost dates near Iron River
- Stambaugh Jun 4 · Sep 10
- Caspian Jun 4 · Sep 10
- Gaastra Jun 4 · Sep 10
- Alpha May 24 · Sep 25
- Amasa Jun 6 · Sep 9
- Crystal Falls Jun 6 · Sep 9
- Channing May 24 · Sep 25
- Sagola May 24 · Sep 25
- Sidnaw May 25 · Sep 25
- Watersmeet May 31 · Sep 19
Frequently asked questions
When is the last frost in Iron River, MI?
The median last spring frost in Iron River, MI is June 4. There is still about a 10% chance of frost after June 26, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Iron River, MI?
The median first fall frost is September 10, with about a 10% chance of frost before August 21.
How long is the growing season in Iron River, MI?
About 98 days between the median last spring frost and first fall frost.
What planting zone is Iron River, MI?
Iron River, MI is in USDA hardiness zone 4a.