Grand Portage, MN frost dates
Last spring frostMay 24median date
First fall frostSep 29median date
Growing season128 daysfrost-free
Hardiness zone4bZone 4b
How Grand Portage compares
- In 8 years out of 10, the last spring frost in Grand Portage falls between May 7 and June 5, a 29-day window. The first fall frost falls between September 16 and October 10.
- The median last frost is 19 days later than the Minnesota median of May 5.
- Its 128-day growing season is longer than 6% of the 801 Minnesota places with a regular frost season (state median 151 days).
- The last frost is 16 days later than the zone 4b median of May 8. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 4b chart.
- The weather station records an average of 196 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 7 |
| 50% (median) | May 24 |
| 10% (safe for tender plants) | June 5 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 16 |
| 50% (median) | September 29 |
| 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 Grand Portage, MN
Grand Portage, MN frost dates — last frost May 24, first frost Sep 29, zone 4b. whenisthelastfrost.com
Crop
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Start indoors: Mar 1 to Mar 15Transplant outside: Apr 26 to May 10
Start indoors: Mar 15 to Mar 29Transplant outside: Jun 7 to Jun 21
Start indoors: Mar 15 to Mar 29Transplant outside: Jun 7 to Jun 21
Start indoors: Mar 29 to Apr 12Transplant outside: May 31 to Jun 14
Start indoors: Mar 29 to Apr 12Transplant outside: May 3 to May 17Sow outdoors: Apr 26 to May 31Plant for fall: Aug 4 to Sep 1
Start indoors: Mar 29 to Apr 12Transplant outside: Apr 26 to May 10Sow outdoors: Apr 26 to May 10Plant for fall: Jul 21 to Aug 11
Start indoors: Mar 29 to Apr 12Transplant outside: May 10 to May 24Plant for fall: Jun 23 to Jul 14
Start indoors: Mar 29 to Apr 12Transplant outside: May 3 to May 17Plant for fall: Jun 23 to Jul 14
Start indoors: Mar 29 to Apr 12Transplant outside: May 10 to May 24Plant for fall: Jun 23 to Jul 14
Start indoors: Apr 12 to Apr 26Transplant outside: Jun 14 to Jun 28Sow outdoors: Jun 14 to Jun 28
Start indoors: Apr 12 to Apr 26Transplant outside: May 31 to Jun 14
Sow outdoors: Apr 12 to May 3Plant for fall: Jul 7 to Jul 28
Sow outdoors: Apr 12 to May 3Plant for fall: Aug 4 to Aug 25
Sow outdoors: Apr 19 to May 31Plant for fall: Aug 18 to Sep 8
Start indoors: Apr 26 to May 3Transplant outside: Jun 7 to Jun 14Sow outdoors: May 31 to Jun 14Plant for fall: Jul 14 to Jul 28
Start indoors: Apr 26 to May 3Sow outdoors: May 31 to Jun 14Plant for fall: Jul 21 to Aug 4
Start indoors: Apr 26 to May 3Sow outdoors: May 31 to Jun 14
Start indoors: Apr 26 to May 3Transplant outside: Jun 7 to Jun 21
Sow outdoors: May 3 to May 31Plant for fall: Jul 7 to Jul 21
Sow outdoors: May 3 to May 31Plant for fall: Jul 21 to Aug 4
Sow outdoors: May 3 to May 24
Sow outdoors: May 10 to Jun 7Plant for fall: Jul 21 to Aug 4
Sow outdoors: May 10 to May 31Plant for fall: Aug 4 to Aug 25
Sow outdoors: May 31 to Jun 21Plant for fall: Jul 14 to Jul 28
Sow outdoors: May 31 to Jun 14
Transplant outside: Jun 7 to Jun 28
Plant for fall: Sep 15 to Oct 20
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Grand Portage, MN
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Mar 1 – Mar 15 | Apr 26 – May 10 | — | — |
| Peppers | Mar 15 – Mar 29 | Jun 7 – Jun 21 | — | — |
| Eggplant | Mar 15 – Mar 29 | Jun 7 – Jun 21 | — | — |
| Tomatoes | Mar 29 – Apr 12 | May 31 – Jun 14 | — | — |
| Lettuce | Mar 29 – Apr 12 | May 3 – May 17 | Apr 26 – May 31 | Aug 4 – Sep 1 |
| Kale | Mar 29 – Apr 12 | Apr 26 – May 10 | Apr 26 – May 10 | Jul 21 – Aug 11 |
| Broccoli | Mar 29 – Apr 12 | May 10 – May 24 | — | Jun 23 – Jul 14 |
| Cabbage | Mar 29 – Apr 12 | May 3 – May 17 | — | Jun 23 – Jul 14 |
| Cauliflower | Mar 29 – Apr 12 | May 10 – May 24 | — | Jun 23 – Jul 14 |
| Okra | Apr 12 – Apr 26 | Jun 14 – Jun 28 | Jun 14 – Jun 28 | — |
| Basil | Apr 12 – Apr 26 | May 31 – Jun 14 | — | — |
| Peas | — | — | Apr 12 – May 3 | Jul 7 – Jul 28 |
| Spinach | — | — | Apr 12 – May 3 | Aug 4 – Aug 25 |
| Radishes | — | — | Apr 19 – May 31 | Aug 18 – Sep 8 |
| Cucumbers | Apr 26 – May 3 | Jun 7 – Jun 14 | May 31 – Jun 14 | Jul 14 – Jul 28 |
| Zucchini & Summer Squash | Apr 26 – May 3 | — | May 31 – Jun 14 | Jul 21 – Aug 4 |
| Winter Squash & Pumpkins | Apr 26 – May 3 | — | May 31 – Jun 14 | — |
| Melons & Watermelon | Apr 26 – May 3 | Jun 7 – Jun 21 | — | — |
| Carrots | — | — | May 3 – May 31 | Jul 7 – Jul 21 |
| Beets | — | — | May 3 – May 31 | Jul 21 – Aug 4 |
| Potatoes | — | — | May 3 – May 24 | — |
| Swiss Chard | — | — | May 10 – Jun 7 | Jul 21 – Aug 4 |
| Cilantro | — | — | May 10 – May 31 | Aug 4 – Aug 25 |
| Green Beans | — | — | May 31 – Jun 21 | Jul 14 – Jul 28 |
| Sweet Corn | — | — | May 31 – Jun 14 | — |
| Sweet Potatoes | — | Jun 7 – Jun 28 | — | — |
| Garlic | — | — | — | Sep 15 – Oct 20 |
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 Grand Portage, MN weather station, about 1 km away (elevation 732 ft (223 m)).
Frost dates near Grand Portage
- Hovland May 20 · Oct 5
- Grand Marais May 20 · Oct 5
- Lutsen May 26 · Sep 27
- Tofte May 26 · Sep 27
- Schroeder May 15 · Oct 1
- Finland May 15 · Oct 1
- Silver Bay May 15 · Oct 1
- Isabella May 31 · Sep 15
- Beaver Bay May 15 · Oct 1
- Winton May 14 · Sep 29
Frequently asked questions
When is the last frost in Grand Portage, MN?
The median last spring frost in Grand Portage, MN is May 24. There is still about a 10% chance of frost after June 5, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Grand Portage, MN?
The median first fall frost is September 29, with about a 10% chance of frost before September 16.
How long is the growing season in Grand Portage, MN?
About 128 days between the median last spring frost and first fall frost.
What planting zone is Grand Portage, MN?
Grand Portage, MN is in USDA hardiness zone 4b.