I suspect it is because in French it is “le sud de France” which translates directly as the south of France. People do sometimes say southern France as well but it is not as common.

I forgot you were studying French. Thank you janbb!

I hear both.

I think @janbb is probably right, it’s because of the language.

Even in English from state to state we use different expressions. New Yorkers say “upstate” while Michiganders say “up north” when talking about northern areas within their same state.

Don’t they also say “the 23rd of September” instead of “September 23rd”?
My high school French teacher said Southern France

“Up north” is a common phrase in Wisconsin too.

In Georgia, we call anything above Tennessee as “Up North”.

@elbanditoroso That throws me off in the South, because if I’m in a Southern state I wouldn’t call the midwestern states North, I’d refer to them as the Midwest.

Probably the same as out west, back east, up north and down south.

My guess would be what @janbb said, but should note that that is the standard phrasing in any Romance language, but we don’t usually say “the south of Italy” or “the south of Spain”. Perhaps the South of France has a little bit more salience to English-speakers, given its reputation as a distinct region and vacation destination. Southern France is also called the “Midi” just as Southern Italy is called the “Mezzogiorno”; both of these names mean “mid-day” and refer to the fact that the sun is in the south at noon in the northern hemisphere.

The South of France means the Mediterranean coast to me.

Southern France would be approximately the southern half.