Isabella, MN frost dates
Last spring frostMay 31median date
First fall frostSep 15median date
Growing season107 daysfrost-free
Hardiness zone3bZone 3b
How Isabella compares
- In 8 years out of 10, the last spring frost in Isabella falls between May 16 and June 21, a 36-day window. The first fall frost falls between August 30 and September 29.
- The median last frost is 26 days later than the Minnesota median of May 5.
- Its 107-day growing season is among the shortest of the 801 Minnesota places with a regular frost season.
- The last frost is 14 days later than the zone 3b median of May 17. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 3b chart.
- The weather station records an average of 206 nights a year at or below 32°F.
- Compared with Duluth, MN, 108 km away, the last frost here is 17 days later than there and the growing season is 44 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 16 |
| 50% (median) | May 31 |
| 10% (safe for tender plants) | June 21 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | August 30 |
| 50% (median) | September 15 |
| 90% (late) | September 29 |
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 Isabella, MN
Isabella, MN frost dates — last frost May 31, first frost Sep 15, zone 3b. whenisthelastfrost.com
Crop
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Start indoors: Mar 8 to Mar 22Transplant outside: May 3 to May 17
Start indoors: Mar 22 to Apr 5Transplant outside: Jun 14 to Jun 28
Start indoors: Mar 22 to Apr 5Transplant outside: Jun 14 to Jun 28
Start indoors: Apr 5 to Apr 19Transplant outside: Jun 7 to Jun 21
Start indoors: Apr 5 to Apr 19Transplant outside: May 10 to May 24Sow outdoors: May 3 to Jun 7Plant for fall: Jul 21 to Aug 18
Start indoors: Apr 5 to Apr 19Transplant outside: May 3 to May 17Sow outdoors: May 3 to May 17Plant for fall: Jul 7 to Jul 28
Start indoors: Apr 5 to Apr 19Transplant outside: May 17 to May 31
Start indoors: Apr 5 to Apr 19Transplant outside: May 10 to May 24
Start indoors: Apr 5 to Apr 19Transplant outside: May 17 to May 31
Start indoors: Apr 19 to May 3Transplant outside: Jun 21 to Jul 5Sow outdoors: Jun 21 to Jul 5
Start indoors: Apr 19 to May 3Transplant outside: Jun 7 to Jun 21
Sow outdoors: Apr 19 to May 10Plant for fall: Jun 23 to Jul 14
Sow outdoors: Apr 19 to May 10Plant for fall: Jul 21 to Aug 11
Sow outdoors: Apr 26 to Jun 7Plant for fall: Aug 4 to Aug 25
Start indoors: May 3 to May 10Transplant outside: Jun 14 to Jun 21Sow outdoors: Jun 7 to Jun 21
Start indoors: May 3 to May 10Sow outdoors: Jun 7 to Jun 21Plant for fall: Jul 7 to Jul 21
Start indoors: May 3 to May 10Sow outdoors: Jun 7 to Jun 21
Start indoors: May 3 to May 10Transplant outside: Jun 14 to Jun 28
Sow outdoors: May 10 to Jun 7Plant for fall: Jun 23 to Jul 7
Sow outdoors: May 10 to Jun 7Plant for fall: Jul 7 to Jul 21
Sow outdoors: May 10 to May 31
Sow outdoors: May 17 to Jun 14Plant for fall: Jul 7 to Jul 21
Sow outdoors: May 17 to Jun 7Plant for fall: Jul 21 to Aug 11
Sow outdoors: Jun 7 to Jun 28
Sow outdoors: Jun 7 to Jun 21
Transplant outside: Jun 14 to Jul 5
Plant for fall: Sep 1 to Oct 6
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Isabella, MN
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Mar 8 – Mar 22 | May 3 – May 17 | — | — |
| Peppers | Mar 22 – Apr 5 | Jun 14 – Jun 28 | — | — |
| Eggplant | Mar 22 – Apr 5 | Jun 14 – Jun 28 | — | — |
| Tomatoes | Apr 5 – Apr 19 | Jun 7 – Jun 21 | — | — |
| Lettuce | Apr 5 – Apr 19 | May 10 – May 24 | May 3 – Jun 7 | Jul 21 – Aug 18 |
| Kale | Apr 5 – Apr 19 | May 3 – May 17 | May 3 – May 17 | Jul 7 – Jul 28 |
| Broccoli | Apr 5 – Apr 19 | May 17 – May 31 | — | — |
| Cabbage | Apr 5 – Apr 19 | May 10 – May 24 | — | — |
| Cauliflower | Apr 5 – Apr 19 | May 17 – May 31 | — | — |
| Okra | Apr 19 – May 3 | Jun 21 – Jul 5 | Jun 21 – Jul 5 | — |
| Basil | Apr 19 – May 3 | Jun 7 – Jun 21 | — | — |
| Peas | — | — | Apr 19 – May 10 | Jun 23 – Jul 14 |
| Spinach | — | — | Apr 19 – May 10 | Jul 21 – Aug 11 |
| Radishes | — | — | Apr 26 – Jun 7 | Aug 4 – Aug 25 |
| Cucumbers | May 3 – May 10 | Jun 14 – Jun 21 | Jun 7 – Jun 21 | — |
| Zucchini & Summer Squash | May 3 – May 10 | — | Jun 7 – Jun 21 | Jul 7 – Jul 21 |
| Winter Squash & Pumpkins Warning: Your frost-free season is about 107 days, which is tight for winter squash & pumpkins (100+ days). Choose early varieties and use transplants or row covers. | May 3 – May 10 | — | Jun 7 – Jun 21 | — |
| Melons & Watermelon | May 3 – May 10 | Jun 14 – Jun 28 | — | — |
| Carrots | — | — | May 10 – Jun 7 | Jun 23 – Jul 7 |
| Beets | — | — | May 10 – Jun 7 | Jul 7 – Jul 21 |
| Potatoes | — | — | May 10 – May 31 | — |
| Swiss Chard | — | — | May 17 – Jun 14 | Jul 7 – Jul 21 |
| Cilantro | — | — | May 17 – Jun 7 | Jul 21 – Aug 11 |
| Green Beans | — | — | Jun 7 – Jun 28 | — |
| Sweet Corn | — | — | Jun 7 – Jun 21 | — |
| Sweet Potatoes Warning: Your frost-free season is about 107 days, which is tight for sweet potatoes (100+ days). Choose early varieties and use transplants or row covers. | — | Jun 14 – Jul 5 | — | — |
| Garlic | — | — | — | Sep 1 – Oct 6 |
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 Isabella 14w, MN weather station, 14 km away (elevation 1,739 ft (530 m)).
Frost dates near Isabella
- Finland May 15 · Oct 1
- Babbitt May 28 · Sep 14
- Winton May 14 · Sep 29
- Ely May 14 · Sep 29
- Silver Bay May 15 · Oct 1
- Schroeder May 15 · Oct 1
- Beaver Bay May 15 · Oct 1
- Brimson frost any month
- Tofte May 26 · Sep 27
- Hoyt Lakes frost any month
Frequently asked questions
When is the last frost in Isabella, MN?
The median last spring frost in Isabella, MN is May 31. There is still about a 10% chance of frost after June 21, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Isabella, MN?
The median first fall frost is September 15, with about a 10% chance of frost before August 30.
How long is the growing season in Isabella, MN?
About 107 days between the median last spring frost and first fall frost.
What planting zone is Isabella, MN?
Isabella, MN is in USDA hardiness zone 3b.