It actually should be called southern Florida.

Why?

South is a direction. Southern is used to describe a region or area.

There's North Carolina and South Carolina and North Dakota and South Dakota. But south Florida isn't a state, it's part of the state of Florida. Let's look at California. Is southern California ever called south California?

I used the phrase south Florida too. I live here. It's just that way.

Now let's look at university names. There's the University of South Florida and The University of North Florida. This makes no sense to me. When did the state divide into two? I guess the University of Central Florida should really be called the University of Center Florida...