Ya’ gotta wonder if the writing for yahoo.com has been outsourced to a country where the residents are totally unfamiliar with U.S. geography. I can’t imagine anyone in the States referring to Southern California as “South California,” can you?
And I don’t know of anyone in the U.S. who would think that this is correct:
When capitalized, Southern refers to the southeastern portion of the United States, where there are no plains. The southern plains refers to the southern part of the Great Plains, generally considered in the center of the country.
Maybe they don’t teach U.S. geography in the country where these were written. Maybe Yahoo! should bring the writing of its site back to the U.S.