Governor Tony Evers declared a Public Health Emergency today, in Executive Order #82, and issued an Emergency Order requiring people to wear face coverings when indoors and not in a private residence.
Executive Order # 82 goes into effect Saturday, and will expire on September 28th. In a press release sent out earlier today, Gov. Evers said that Wisconsin is "seeing new and significant community spread and increases in cases of COVID-19 which require the public health emergency and require face coverings."
You can red Executive Order #82 here; and Emergency Order #1 here.