City	Sow outdoors	Last frost
Milwaukee	Apr 12 to May 10	Apr 26
Madison	Apr 17 to May 15	May 1
Green Bay	Apr 23 to May 21	May 7
Kenosha	Apr 14 to May 12	Apr 28
Racine	Apr 6 to May 4	Apr 20
Appleton	Apr 20 to May 18	May 4
Eau Claire	Apr 10 to May 8	Apr 24
Waukesha	Apr 17 to May 15	May 1
Oshkosh	Apr 10 to May 8	Apr 24
Janesville	Apr 12 to May 10	Apr 26
West Allis	Apr 12 to May 10	Apr 26
La Crosse	Apr 13 to May 11	Apr 27
Sheboygan	Apr 11 to May 9	Apr 25
Wauwatosa	Apr 12 to May 10	Apr 26
Fond du Lac	Apr 13 to May 11	Apr 27
Brookfield	Apr 16 to May 14	Apr 30
Menomonee Falls	Apr 22 to May 20	May 6
Wausau	Apr 22 to May 20	May 6
New Berlin	Apr 19 to May 17	May 3
Sun Prairie	Apr 17 to May 15	May 1
Oak Creek	Apr 8 to May 6	Apr 22
Greenfield	Apr 19 to May 17	May 3
Franklin	Apr 19 to May 17	May 3
Beloit	Apr 17 to May 15	May 1
Manitowoc	Apr 16 to May 14	Apr 30
Fitchburg	Apr 17 to May 15	May 1
West Bend	Apr 17 to May 15	May 1
Mount Pleasant	Apr 6 to May 4	Apr 20
Neenah	Apr 20 to May 18	May 4
Superior	Apr 22 to May 20	May 6
Stevens Point	Apr 20 to May 18	May 4
Muskego	Apr 19 to May 17	May 3
De Pere	Apr 16 to May 14	Apr 30
Caledonia	Apr 10 to May 8	Apr 24
Mequon	Apr 22 to May 20	May 6
Middleton	Apr 14 to May 12	Apr 28
Watertown	Apr 14 to May 12	Apr 28
Howard	Apr 23 to May 21	May 7
Pleasant Prairie	Apr 5 to May 3	Apr 19
Germantown	Apr 22 to May 20	May 6
Onalaska	Apr 9 to May 7	Apr 23
South Milwaukee	Apr 8 to May 6	Apr 22
Oconomowoc	Apr 16 to May 14	Apr 30

Questions

When should I plant swiss chard in Wisconsin?

In Milwaukee, sow outdoors from April 12 to May 10. Across Wisconsin the window opens between April 5 and April 23, depending on the local last frost.

How is this date worked out?

Sow outdoors from 2 weeks before to 2 weeks after the last frost. Frost dates are NOAA 1991–2020 averages for the weather station nearest each city.