Wis. Stat. § 180.0822: Notice of meeting.

(1) Unless the articles of incorporation or bylaws provide otherwise, regular meetings of the board of directors may be held without notice of the date, time, place or purpose of the meeting.

(2) Except as provided in s. 180.0303 (3), and unless the articles of incorporation or bylaws provide for a longer or shorter period, special meetings of the board of directors shall be preceded by at least 48 hours’ notice of the date, time and place of the meeting. The notice shall comply with s. 180.0141. The notice need not describe the purpose of the special meeting unless required by the articles of incorporation or bylaws.