The Coastal Plain portion of this type is characterized by marine terraces, on the seaward side of which are often found fossilized sand dunes. This type is also characterized by bays, sounds, barrier islands, and wide estuaries. Along the coasts in Florida and the Carolinas, the terraces are poorly drained and may be saturated for part of the year.
Inland terraces are narrower and more dissected than coastal terraces.
This area has the highest frequency of heavy downpours combined with the most rain-free days per year. In the eastern part of this region precipitation is lowest in the fall and highest in midsummer. The southern mixed forest is subjected to annual hurricanes, especially along peninsular Florida and the Gulf Coast. The southern mixed forest experiences mild winters. Frost-free days occur from April first to November first, and the growing season usually exceeds 210 days.