Grantsburg, WI frost dates
Last spring frostMay 11median date
First fall frostOct 1median date
Growing season143 daysfrost-free
Hardiness zone4aZone 4a
How Grantsburg compares
- In 8 years out of 10, the last spring frost in Grantsburg falls between April 27 and May 28, a 31-day window. The first fall frost falls between September 16 and October 14.
- The median last frost is 6 days later than the Wisconsin median of May 5.
- Its 143-day growing season is longer than 20% of the 749 Wisconsin places with a regular frost season (state median 155 days).
- The last frost is typical for zone 4a, where the median is May 12.
- The weather station records an average of 177 nights a year at or below 32°F.
- Compared with Saint Paul, MN, 98 km away, the last frost here is 17 days later than there and the growing season is 32 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 27 |
| 50% (median) | May 11 |
| 10% (safe for tender plants) | May 28 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 16 |
| 50% (median) | October 1 |
| 90% (late) | October 14 |
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 Grantsburg, WI
Grantsburg, WI frost dates — last frost May 11, first frost Oct 1, zone 4a. whenisthelastfrost.com
Crop
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Start indoors: Feb 16 to Mar 2Transplant outside: Apr 13 to Apr 27
Start indoors: Mar 2 to Mar 16Transplant outside: May 25 to Jun 8
Start indoors: Mar 2 to Mar 16Transplant outside: May 25 to Jun 8
Start indoors: Mar 16 to Mar 30Transplant outside: May 18 to Jun 1
Start indoors: Mar 16 to Mar 30Transplant outside: Apr 20 to May 4Sow outdoors: Apr 13 to May 18Plant for fall: Aug 6 to Sep 3
Start indoors: Mar 16 to Mar 30Transplant outside: Apr 13 to Apr 27Sow outdoors: Apr 13 to Apr 27Plant for fall: Jul 23 to Aug 13
Start indoors: Mar 16 to Mar 30Transplant outside: Apr 27 to May 11Plant for fall: Jun 25 to Jul 16
Start indoors: Mar 16 to Mar 30Transplant outside: Apr 20 to May 4Plant for fall: Jun 25 to Jul 16
Start indoors: Mar 16 to Mar 30Transplant outside: Apr 27 to May 11Plant for fall: Jun 25 to Jul 16
Start indoors: Mar 30 to Apr 13Transplant outside: Jun 1 to Jun 15Sow outdoors: Jun 1 to Jun 15
Start indoors: Mar 30 to Apr 13Transplant outside: May 18 to Jun 1
Sow outdoors: Mar 30 to Apr 20Plant for fall: Jul 9 to Jul 30
Sow outdoors: Mar 30 to Apr 20Plant for fall: Aug 6 to Aug 27
Sow outdoors: Apr 6 to May 18Plant for fall: Aug 20 to Sep 10
Start indoors: Apr 13 to Apr 20Transplant outside: May 25 to Jun 1Sow outdoors: May 18 to Jun 1Plant for fall: Jul 16 to Jul 30
Start indoors: Apr 13 to Apr 20Sow outdoors: May 18 to Jun 1Plant for fall: Jul 23 to Aug 6
Start indoors: Apr 13 to Apr 20Sow outdoors: May 18 to Jun 1
Start indoors: Apr 13 to Apr 20Transplant outside: May 25 to Jun 8
Sow outdoors: Apr 20 to May 18Plant for fall: Jul 9 to Jul 23
Sow outdoors: Apr 20 to May 18Plant for fall: Jul 23 to Aug 6
Sow outdoors: Apr 20 to May 11
Sow outdoors: Apr 27 to May 25Plant for fall: Jul 23 to Aug 6
Sow outdoors: Apr 27 to May 18Plant for fall: Aug 6 to Aug 27
Sow outdoors: May 18 to Jun 8Plant for fall: Jul 16 to Jul 30
Sow outdoors: May 18 to Jun 1
Transplant outside: May 25 to Jun 15
Plant for fall: Sep 17 to Oct 22
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Grantsburg, WI
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 16 – Mar 2 | Apr 13 – Apr 27 | — | — |
| Peppers | Mar 2 – Mar 16 | May 25 – Jun 8 | — | — |
| Eggplant | Mar 2 – Mar 16 | May 25 – Jun 8 | — | — |
| Tomatoes | Mar 16 – Mar 30 | May 18 – Jun 1 | — | — |
| Lettuce | Mar 16 – Mar 30 | Apr 20 – May 4 | Apr 13 – May 18 | Aug 6 – Sep 3 |
| Kale | Mar 16 – Mar 30 | Apr 13 – Apr 27 | Apr 13 – Apr 27 | Jul 23 – Aug 13 |
| Broccoli | Mar 16 – Mar 30 | Apr 27 – May 11 | — | Jun 25 – Jul 16 |
| Cabbage | Mar 16 – Mar 30 | Apr 20 – May 4 | — | Jun 25 – Jul 16 |
| Cauliflower | Mar 16 – Mar 30 | Apr 27 – May 11 | — | Jun 25 – Jul 16 |
| Okra | Mar 30 – Apr 13 | Jun 1 – Jun 15 | Jun 1 – Jun 15 | — |
| Basil | Mar 30 – Apr 13 | May 18 – Jun 1 | — | — |
| Peas | — | — | Mar 30 – Apr 20 | Jul 9 – Jul 30 |
| Spinach | — | — | Mar 30 – Apr 20 | Aug 6 – Aug 27 |
| Radishes | — | — | Apr 6 – May 18 | Aug 20 – Sep 10 |
| Cucumbers | Apr 13 – Apr 20 | May 25 – Jun 1 | May 18 – Jun 1 | Jul 16 – Jul 30 |
| Zucchini & Summer Squash | Apr 13 – Apr 20 | — | May 18 – Jun 1 | Jul 23 – Aug 6 |
| Winter Squash & Pumpkins | Apr 13 – Apr 20 | — | May 18 – Jun 1 | — |
| Melons & Watermelon | Apr 13 – Apr 20 | May 25 – Jun 8 | — | — |
| Carrots | — | — | Apr 20 – May 18 | Jul 9 – Jul 23 |
| Beets | — | — | Apr 20 – May 18 | Jul 23 – Aug 6 |
| Potatoes | — | — | Apr 20 – May 11 | — |
| Swiss Chard | — | — | Apr 27 – May 25 | Jul 23 – Aug 6 |
| Cilantro | — | — | Apr 27 – May 18 | Aug 6 – Aug 27 |
| Green Beans | — | — | May 18 – Jun 8 | Jul 16 – Jul 30 |
| Sweet Corn | — | — | May 18 – Jun 1 | — |
| Sweet Potatoes | — | May 25 – Jun 15 | — | — |
| 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 Grantsburg, WI weather station, 3 km away (elevation 991 ft (302 m)).
Frost dates near Grantsburg
- Siren May 11 · Oct 1
- Cushing May 19 · Sep 25
- Frederic May 6 · Oct 4
- Webster May 11 · Sep 30
- Saint Croix Falls May 19 · Sep 25
- Milltown May 6 · Oct 4
- Luck May 6 · Oct 4
- Danbury May 11 · Sep 30
- Centuria May 4 · Oct 8
- Hertel May 14 · Sep 28
Frequently asked questions
When is the last frost in Grantsburg, WI?
The median last spring frost in Grantsburg, WI is May 11. There is still about a 10% chance of frost after May 28, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Grantsburg, WI?
The median first fall frost is October 1, with about a 10% chance of frost before September 16.
How long is the growing season in Grantsburg, WI?
About 143 days between the median last spring frost and first fall frost.
What planting zone is Grantsburg, WI?
Grantsburg, WI is in USDA hardiness zone 4a.