Ontonagon, MI frost dates
Last spring frostMay 27median date
First fall frostOct 1median date
Growing season127 daysfrost-free
Hardiness zone5aZone 5a
How Ontonagon compares
- In 8 years out of 10, the last spring frost in Ontonagon falls between May 7 and June 13, a 37-day window. The first fall frost falls between September 14 and October 16.
- The median last frost is 22 days later than the Michigan median of May 5.
- Its 127-day growing season is longer than 7% of the 878 Michigan places with a regular frost season (state median 162 days).
- The last frost is 24 days later than the zone 5a median of May 3. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5a chart.
- The weather station records an average of 175 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 7 |
| 50% (median) | May 27 |
| 10% (safe for tender plants) | June 13 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 14 |
| 50% (median) | October 1 |
| 90% (late) | October 16 |
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 Ontonagon, MI
Ontonagon, MI frost dates — last frost May 27, first frost Oct 1, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Mar 4 to Mar 18Transplant outside: Apr 29 to May 13
Start indoors: Mar 18 to Apr 1Transplant outside: Jun 10 to Jun 24
Start indoors: Mar 18 to Apr 1Transplant outside: Jun 10 to Jun 24
Start indoors: Apr 1 to Apr 15Transplant outside: Jun 3 to Jun 17
Start indoors: Apr 1 to Apr 15Transplant outside: May 6 to May 20Sow outdoors: Apr 29 to Jun 3Plant for fall: Aug 6 to Sep 3
Start indoors: Apr 1 to Apr 15Transplant outside: Apr 29 to May 13Sow outdoors: Apr 29 to May 13Plant for fall: Jul 23 to Aug 13
Start indoors: Apr 1 to Apr 15Transplant outside: May 13 to May 27Plant for fall: Jun 25 to Jul 16
Start indoors: Apr 1 to Apr 15Transplant outside: May 6 to May 20Plant for fall: Jun 25 to Jul 16
Start indoors: Apr 1 to Apr 15Transplant outside: May 13 to May 27Plant for fall: Jun 25 to Jul 16
Start indoors: Apr 15 to Apr 29Transplant outside: Jun 17 to Jul 1Sow outdoors: Jun 17 to Jul 1
Start indoors: Apr 15 to Apr 29Transplant outside: Jun 3 to Jun 17
Sow outdoors: Apr 15 to May 6Plant for fall: Jul 9 to Jul 30
Sow outdoors: Apr 15 to May 6Plant for fall: Aug 6 to Aug 27
Sow outdoors: Apr 22 to Jun 3Plant for fall: Aug 20 to Sep 10
Start indoors: Apr 29 to May 6Transplant outside: Jun 10 to Jun 17Sow outdoors: Jun 3 to Jun 17Plant for fall: Jul 16 to Jul 30
Start indoors: Apr 29 to May 6Sow outdoors: Jun 3 to Jun 17Plant for fall: Jul 23 to Aug 6
Start indoors: Apr 29 to May 6Sow outdoors: Jun 3 to Jun 17
Start indoors: Apr 29 to May 6Transplant outside: Jun 10 to Jun 24
Sow outdoors: May 6 to Jun 3Plant for fall: Jul 9 to Jul 23
Sow outdoors: May 6 to Jun 3Plant for fall: Jul 23 to Aug 6
Sow outdoors: May 6 to May 27
Sow outdoors: May 13 to Jun 10Plant for fall: Jul 23 to Aug 6
Sow outdoors: May 13 to Jun 3Plant for fall: Aug 6 to Aug 27
Sow outdoors: Jun 3 to Jun 24Plant for fall: Jul 16 to Jul 30
Sow outdoors: Jun 3 to Jun 17
Transplant outside: Jun 10 to Jul 1
Plant for fall: Sep 17 to Oct 22
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Ontonagon, MI
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Mar 4 – Mar 18 | Apr 29 – May 13 | — | — |
| Peppers | Mar 18 – Apr 1 | Jun 10 – Jun 24 | — | — |
| Eggplant | Mar 18 – Apr 1 | Jun 10 – Jun 24 | — | — |
| Tomatoes | Apr 1 – Apr 15 | Jun 3 – Jun 17 | — | — |
| Lettuce | Apr 1 – Apr 15 | May 6 – May 20 | Apr 29 – Jun 3 | Aug 6 – Sep 3 |
| Kale | Apr 1 – Apr 15 | Apr 29 – May 13 | Apr 29 – May 13 | Jul 23 – Aug 13 |
| Broccoli | Apr 1 – Apr 15 | May 13 – May 27 | — | Jun 25 – Jul 16 |
| Cabbage | Apr 1 – Apr 15 | May 6 – May 20 | — | Jun 25 – Jul 16 |
| Cauliflower | Apr 1 – Apr 15 | May 13 – May 27 | — | Jun 25 – Jul 16 |
| Okra | Apr 15 – Apr 29 | Jun 17 – Jul 1 | Jun 17 – Jul 1 | — |
| Basil | Apr 15 – Apr 29 | Jun 3 – Jun 17 | — | — |
| Peas | — | — | Apr 15 – May 6 | Jul 9 – Jul 30 |
| Spinach | — | — | Apr 15 – May 6 | Aug 6 – Aug 27 |
| Radishes | — | — | Apr 22 – Jun 3 | Aug 20 – Sep 10 |
| Cucumbers | Apr 29 – May 6 | Jun 10 – Jun 17 | Jun 3 – Jun 17 | Jul 16 – Jul 30 |
| Zucchini & Summer Squash | Apr 29 – May 6 | — | Jun 3 – Jun 17 | Jul 23 – Aug 6 |
| Winter Squash & Pumpkins | Apr 29 – May 6 | — | Jun 3 – Jun 17 | — |
| Melons & Watermelon | Apr 29 – May 6 | Jun 10 – Jun 24 | — | — |
| Carrots | — | — | May 6 – Jun 3 | Jul 9 – Jul 23 |
| Beets | — | — | May 6 – Jun 3 | Jul 23 – Aug 6 |
| Potatoes | — | — | May 6 – May 27 | — |
| Swiss Chard | — | — | May 13 – Jun 10 | Jul 23 – Aug 6 |
| Cilantro | — | — | May 13 – Jun 3 | Aug 6 – Aug 27 |
| Green Beans | — | — | Jun 3 – Jun 24 | Jul 16 – Jul 30 |
| Sweet Corn | — | — | Jun 3 – Jun 17 | — |
| Sweet Potatoes | — | Jun 10 – Jul 1 | — | — |
| Garlic | — | — | — | Sep 17 – Oct 22 |
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 Ontonagon 6 Se, MI weather station, 11 km away (elevation 791 ft (241 m)).
Frost dates near Ontonagon
- Rockland May 27 · Oct 1
- Greenland May 27 · Oct 1
- White Pine May 26 · Sep 27
- Mass City May 23 · Oct 1
- Ewen May 26 · Sep 27
- Bergland May 26 · Sep 27
- Bruce Crossing May 31 · Sep 19
- Nisula May 23 · Oct 1
- Toivola May 23 · Oct 1
- Trout Creek May 31 · Sep 19
Frequently asked questions
When is the last frost in Ontonagon, MI?
The median last spring frost in Ontonagon, MI is May 27. 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 Ontonagon, MI?
The median first fall frost is October 1, with about a 10% chance of frost before September 14.
How long is the growing season in Ontonagon, MI?
About 127 days between the median last spring frost and first fall frost.
What planting zone is Ontonagon, MI?
Ontonagon, MI is in USDA hardiness zone 5a.