Sullivan, WI frost dates
Last spring frostMay 3median date
First fall frostOct 9median date
Growing season159 daysfrost-free
Hardiness zone5bZone 5b
How Sullivan compares
- In 8 years out of 10, the last spring frost in Sullivan falls between April 18 and May 21, a 33-day window. The first fall frost falls between September 25 and October 25.
- The median last frost is 2 days earlier than the Wisconsin median of May 5.
- Its 159-day growing season is longer than 62% of the 749 Wisconsin places with a regular frost season (state median 155 days).
- The last frost is typical for zone 5b, where the median is May 1.
- The weather station records an average of 148 nights a year at or below 32°F.
- Compared with Waukesha, WI, 28 km away, the last frost here is 2 days later than there and the growing season is 6 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 18 |
| 50% (median) | May 3 |
| 10% (safe for tender plants) | May 21 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 25 |
| 50% (median) | October 9 |
| 90% (late) | October 25 |
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 Sullivan, WI
Sullivan, WI frost dates — last frost May 3, first frost Oct 9, zone 5b. whenisthelastfrost.com
Crop
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Start indoors: Feb 8 to Feb 22Transplant outside: Apr 5 to Apr 19
Start indoors: Feb 22 to Mar 8Transplant outside: May 17 to May 31
Start indoors: Feb 22 to Mar 8Transplant outside: May 17 to May 31
Start indoors: Mar 8 to Mar 22Transplant outside: May 10 to May 24
Start indoors: Mar 8 to Mar 22Transplant outside: Apr 12 to Apr 26Sow outdoors: Apr 5 to May 10Plant for fall: Aug 14 to Sep 11
Start indoors: Mar 8 to Mar 22Transplant outside: Apr 5 to Apr 19Sow outdoors: Apr 5 to Apr 19Plant for fall: Jul 31 to Aug 21
Start indoors: Mar 8 to Mar 22Transplant outside: Apr 19 to May 3Plant for fall: Jul 3 to Jul 24
Start indoors: Mar 8 to Mar 22Transplant outside: Apr 12 to Apr 26Plant for fall: Jul 3 to Jul 24
Start indoors: Mar 8 to Mar 22Transplant outside: Apr 19 to May 3Plant for fall: Jul 3 to Jul 24
Start indoors: Mar 22 to Apr 5Transplant outside: May 24 to Jun 7Sow outdoors: May 24 to Jun 7
Start indoors: Mar 22 to Apr 5Transplant outside: May 10 to May 24
Sow outdoors: Mar 22 to Apr 12Plant for fall: Jul 17 to Aug 7
Sow outdoors: Mar 22 to Apr 12Plant for fall: Aug 14 to Sep 4
Sow outdoors: Mar 29 to May 10Plant for fall: Aug 28 to Sep 18
Start indoors: Apr 5 to Apr 12Transplant outside: May 17 to May 24Sow outdoors: May 10 to May 24Plant for fall: Jul 24 to Aug 7
Start indoors: Apr 5 to Apr 12Sow outdoors: May 10 to May 24Plant for fall: Jul 31 to Aug 14
Start indoors: Apr 5 to Apr 12Sow outdoors: May 10 to May 24
Start indoors: Apr 5 to Apr 12Transplant outside: May 17 to May 31
Sow outdoors: Apr 12 to May 10Plant for fall: Jul 17 to Jul 31
Sow outdoors: Apr 12 to May 10Plant for fall: Jul 31 to Aug 14
Sow outdoors: Apr 12 to May 3
Sow outdoors: Apr 19 to May 17Plant for fall: Jul 31 to Aug 14
Sow outdoors: Apr 19 to May 10Plant for fall: Aug 14 to Sep 4
Sow outdoors: May 10 to May 31Plant for fall: Jul 24 to Aug 7
Sow outdoors: May 10 to May 24
Transplant outside: May 17 to Jun 7
Plant for fall: Sep 25 to Oct 30
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Sullivan, WI
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 8 – Feb 22 | Apr 5 – Apr 19 | — | — |
| Peppers | Feb 22 – Mar 8 | May 17 – May 31 | — | — |
| Eggplant | Feb 22 – Mar 8 | May 17 – May 31 | — | — |
| Tomatoes | Mar 8 – Mar 22 | May 10 – May 24 | — | — |
| Lettuce | Mar 8 – Mar 22 | Apr 12 – Apr 26 | Apr 5 – May 10 | Aug 14 – Sep 11 |
| Kale | Mar 8 – Mar 22 | Apr 5 – Apr 19 | Apr 5 – Apr 19 | Jul 31 – Aug 21 |
| Broccoli | Mar 8 – Mar 22 | Apr 19 – May 3 | — | Jul 3 – Jul 24 |
| Cabbage | Mar 8 – Mar 22 | Apr 12 – Apr 26 | — | Jul 3 – Jul 24 |
| Cauliflower | Mar 8 – Mar 22 | Apr 19 – May 3 | — | Jul 3 – Jul 24 |
| Okra | Mar 22 – Apr 5 | May 24 – Jun 7 | May 24 – Jun 7 | — |
| Basil | Mar 22 – Apr 5 | May 10 – May 24 | — | — |
| Peas | — | — | Mar 22 – Apr 12 | Jul 17 – Aug 7 |
| Spinach | — | — | Mar 22 – Apr 12 | Aug 14 – Sep 4 |
| Radishes | — | — | Mar 29 – May 10 | Aug 28 – Sep 18 |
| Cucumbers | Apr 5 – Apr 12 | May 17 – May 24 | May 10 – May 24 | Jul 24 – Aug 7 |
| Zucchini & Summer Squash | Apr 5 – Apr 12 | — | May 10 – May 24 | Jul 31 – Aug 14 |
| Winter Squash & Pumpkins | Apr 5 – Apr 12 | — | May 10 – May 24 | — |
| Melons & Watermelon | Apr 5 – Apr 12 | May 17 – May 31 | — | — |
| Carrots | — | — | Apr 12 – May 10 | Jul 17 – Jul 31 |
| Beets | — | — | Apr 12 – May 10 | Jul 31 – Aug 14 |
| Potatoes | — | — | Apr 12 – May 3 | — |
| Swiss Chard | — | — | Apr 19 – May 17 | Jul 31 – Aug 14 |
| Cilantro | — | — | Apr 19 – May 10 | Aug 14 – Sep 4 |
| Green Beans | — | — | May 10 – May 31 | Jul 24 – Aug 7 |
| Sweet Corn | — | — | May 10 – May 24 | — |
| Sweet Potatoes | — | May 17 – Jun 7 | — | — |
| Garlic | — | — | — | Sep 25 – Oct 30 |
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 Sullivan 3se, WI weather station, 6 km away (elevation 932 ft (284 m)).
Frost dates near Sullivan
- Helenville Apr 25 · Oct 18
- Dousman May 3 · Oct 9
- Palmyra May 3 · Oct 9
- Oconomowoc Apr 30 · Oct 12
- Jefferson Apr 25 · Oct 18
- Ixonia Apr 30 · Oct 12
- Johnson Creek Apr 25 · Oct 18
- Eagle May 3 · Oct 9
- Delafield Apr 30 · Oct 12
- North Prairie May 3 · Oct 9
Frequently asked questions
When is the last frost in Sullivan, WI?
The median last spring frost in Sullivan, WI is May 3. There is still about a 10% chance of frost after May 21, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Sullivan, WI?
The median first fall frost is October 9, with about a 10% chance of frost before September 25.
How long is the growing season in Sullivan, WI?
About 159 days between the median last spring frost and first fall frost.
What planting zone is Sullivan, WI?
Sullivan, WI is in USDA hardiness zone 5b.