Copper Harbor, MI frost dates
Last spring frostMay 10median date
First fall frostOct 21median date
Growing season164 daysfrost-free
Hardiness zone6aZone 6a
How Copper Harbor compares
- In 8 years out of 10, the last spring frost in Copper Harbor falls between April 26 and June 2, a 37-day window. The first fall frost falls between October 3 and November 5.
- The median last frost is 5 days later than the Michigan median of May 5.
- Its 164-day growing season is longer than 57% of the 878 Michigan places with a regular frost season (state median 162 days).
- The last frost is 11 days later than the zone 6a median of Apr 29. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 6a chart.
- The weather station records an average of 152 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 26 |
| 50% (median) | May 10 |
| 10% (safe for tender plants) | June 2 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 3 |
| 50% (median) | October 21 |
| 90% (late) | November 5 |
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 Copper Harbor, MI
Copper Harbor, MI frost dates — last frost May 10, first frost Oct 21, zone 6a. whenisthelastfrost.com
Crop
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Start indoors: Feb 15 to Mar 1Transplant outside: Apr 12 to Apr 26
Start indoors: Mar 1 to Mar 15Transplant outside: May 24 to Jun 7
Start indoors: Mar 1 to Mar 15Transplant outside: May 24 to Jun 7
Start indoors: Mar 15 to Mar 29Transplant outside: May 17 to May 31
Start indoors: Mar 15 to Mar 29Transplant outside: Apr 19 to May 3Sow outdoors: Apr 12 to May 17Plant for fall: Aug 26 to Sep 23
Start indoors: Mar 15 to Mar 29Transplant outside: Apr 12 to Apr 26Sow outdoors: Apr 12 to Apr 26Plant for fall: Aug 12 to Sep 2
Start indoors: Mar 15 to Mar 29Transplant outside: Apr 26 to May 10Plant for fall: Jul 15 to Aug 5
Start indoors: Mar 15 to Mar 29Transplant outside: Apr 19 to May 3Plant for fall: Jul 15 to Aug 5
Start indoors: Mar 15 to Mar 29Transplant outside: Apr 26 to May 10Plant for fall: Jul 15 to Aug 5
Start indoors: Mar 29 to Apr 12Transplant outside: May 31 to Jun 14Sow outdoors: May 31 to Jun 14
Start indoors: Mar 29 to Apr 12Transplant outside: May 17 to May 31
Sow outdoors: Mar 29 to Apr 19Plant for fall: Jul 29 to Aug 19
Sow outdoors: Mar 29 to Apr 19Plant for fall: Aug 26 to Sep 16
Sow outdoors: Apr 5 to May 17Plant for fall: Sep 9 to Sep 30
Start indoors: Apr 12 to Apr 19Transplant outside: May 24 to May 31Sow outdoors: May 17 to May 31Plant for fall: Aug 5 to Aug 19
Start indoors: Apr 12 to Apr 19Sow outdoors: May 17 to May 31Plant for fall: Aug 12 to Aug 26
Start indoors: Apr 12 to Apr 19Sow outdoors: May 17 to May 31
Start indoors: Apr 12 to Apr 19Transplant outside: May 24 to Jun 7
Sow outdoors: Apr 19 to May 17Plant for fall: Jul 29 to Aug 12
Sow outdoors: Apr 19 to May 17Plant for fall: Aug 12 to Aug 26
Sow outdoors: Apr 19 to May 10
Sow outdoors: Apr 26 to May 24Plant for fall: Aug 12 to Aug 26
Sow outdoors: Apr 26 to May 17Plant for fall: Aug 26 to Sep 16
Sow outdoors: May 17 to Jun 7Plant for fall: Aug 5 to Aug 19
Sow outdoors: May 17 to May 31
Transplant outside: May 24 to Jun 14
Plant for fall: Oct 7 to Nov 11
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Copper Harbor, MI
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 15 – Mar 1 | Apr 12 – Apr 26 | — | — |
| Peppers | Mar 1 – Mar 15 | May 24 – Jun 7 | — | — |
| Eggplant | Mar 1 – Mar 15 | May 24 – Jun 7 | — | — |
| Tomatoes | Mar 15 – Mar 29 | May 17 – May 31 | — | — |
| Lettuce | Mar 15 – Mar 29 | Apr 19 – May 3 | Apr 12 – May 17 | Aug 26 – Sep 23 |
| Kale | Mar 15 – Mar 29 | Apr 12 – Apr 26 | Apr 12 – Apr 26 | Aug 12 – Sep 2 |
| Broccoli | Mar 15 – Mar 29 | Apr 26 – May 10 | — | Jul 15 – Aug 5 |
| Cabbage | Mar 15 – Mar 29 | Apr 19 – May 3 | — | Jul 15 – Aug 5 |
| Cauliflower | Mar 15 – Mar 29 | Apr 26 – May 10 | — | Jul 15 – Aug 5 |
| Okra | Mar 29 – Apr 12 | May 31 – Jun 14 | May 31 – Jun 14 | — |
| Basil | Mar 29 – Apr 12 | May 17 – May 31 | — | — |
| Peas | — | — | Mar 29 – Apr 19 | Jul 29 – Aug 19 |
| Spinach | — | — | Mar 29 – Apr 19 | Aug 26 – Sep 16 |
| Radishes | — | — | Apr 5 – May 17 | Sep 9 – Sep 30 |
| Cucumbers | Apr 12 – Apr 19 | May 24 – May 31 | May 17 – May 31 | Aug 5 – Aug 19 |
| Zucchini & Summer Squash | Apr 12 – Apr 19 | — | May 17 – May 31 | Aug 12 – Aug 26 |
| Winter Squash & Pumpkins | Apr 12 – Apr 19 | — | May 17 – May 31 | — |
| Melons & Watermelon | Apr 12 – Apr 19 | May 24 – Jun 7 | — | — |
| Carrots | — | — | Apr 19 – May 17 | Jul 29 – Aug 12 |
| Beets | — | — | Apr 19 – May 17 | Aug 12 – Aug 26 |
| Potatoes | — | — | Apr 19 – May 10 | — |
| Swiss Chard | — | — | Apr 26 – May 24 | Aug 12 – Aug 26 |
| Cilantro | — | — | Apr 26 – May 17 | Aug 26 – Sep 16 |
| Green Beans | — | — | May 17 – Jun 7 | Aug 5 – Aug 19 |
| Sweet Corn | — | — | May 17 – May 31 | — |
| Sweet Potatoes | — | May 24 – Jun 14 | — | — |
| Garlic | — | — | — | Oct 7 – Nov 11 |
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 Copper Harbor, MI weather station, about 1 km away (elevation 627 ft (191 m)).
Frost dates near Copper Harbor
- Mohawk May 17 · Oct 1
- Ahmeek May 17 · Oct 1
- Copper City May 17 · Oct 1
- Allouez May 17 · Oct 1
- Lake Linden May 17 · Oct 1
- Kearsarge May 17 · Oct 1
- Calumet May 17 · Oct 1
- Hubbell May 17 · Oct 1
- Dollar Bay May 17 · Oct 1
- Hancock May 17 · Oct 1
Frequently asked questions
When is the last frost in Copper Harbor, MI?
The median last spring frost in Copper Harbor, MI is May 10. There is still about a 10% chance of frost after June 2, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Copper Harbor, MI?
The median first fall frost is October 21, with about a 10% chance of frost before October 3.
How long is the growing season in Copper Harbor, MI?
About 164 days between the median last spring frost and first fall frost.
What planting zone is Copper Harbor, MI?
Copper Harbor, MI is in USDA hardiness zone 6a.