Lansing in "Southern Michigan"?
I think not. What is the source or justification for this apparently arbitrary decision? I say "apparently arbitrary" because I can find no evidence that the regions of Michigan are official governmental designations.

 The media (Lansing State Journal, and TV Stations WLNS, WILX, WSYM)
all refer to Lansing as being in Mid-Michigan.

 A Google search for the terms Lansing and "Mid Michigan" turns up many hits that would lead one to believe that Lansing is a part of "Mid-Michigan.

 Conversely, a Google search for Lansing and "Southern Michigan" turns up mostly references where Lansing happens to be mentioned in the same work as a reference to something outside of the Lansing area (in Southern Michigan).

 There are a number of businesses and organizations based in Lansing with "Mid-Michigan" in their title. In the Lansing phone book, I find at least 50 businesses listed whose name begins with "Mid-Michigan" (or "Mid Michigan"). I find one whose name begins with "Southern Michigan".

I would argue that the boundary between "Mid" (or Central) and "Southern" Michigan lies somewhere south of Lansing and somewhere just north of Jackson. Perhaps [Leslie, Michigan|Leslie]] is nearer the border. I believe that once could safely draw the border to include all of Ingham County.

On these grounds, I suggest that in the name of factual accuracy, Lansing be moved (at least in Wikipedia) from "Southern Michigan" to "Central Michigan" (for which "Mid-Michigan" is said to be a synonym).