I checked the Wikipedia using the term 'southeast' region...
According to Wiki the region known as the Southeast USA usually refers to the states:
Tennessee,
North Carolina,
South Carolina,
Georgia,
Florida,
Mississippi and
Alabama.
That being said it sometimes includes:
Delaware,
Maryland,
Virginia,
West Virginia,
Kentucky,
Arkansas and
Louisiana.
There will always be some overlap and each gardener knows best where they fit in climate-wise. Speaking only for myself I know that my climate in Savannah is much different than that of Atlanta.
I'm sure we will welcome any and all folks who want to help keep the Southeast Gardening Region Forum jumping.