Warm-season grasses are originally from tropical regions, which is why they thrive in the scorching sun and high temperatures of the Southern US. Warm-season grasses grow best when temperatures are between 75-90°F and do most of their growing in the summer. In the cooler weather of late-fall and winter, they go dormant, turn brown, and won't green up again until warmer weather returns in spring. The major grasses in this category are bahiagrass, bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass.
Bahiagrass and St. Augustinegrass are found primarily in the Gulf States where the soil is sandy and the air is salty. St. Augustinegrass is also can be found in Southern California. Bahiagrass grows best along the Gulf Coast and Southern Atlantic coastline where it is commonly found. Bermudagrass and zoysiagrass are common throughout the south and into the Transition Zone (the area between the North and South where both cool- and warm-season grasses are found). Centipedegrass is found primarily in the southeast and is popular as a low-maintenance grass.
Since most warm-season grasses go dormant and turn brown over the winter, some people choose to overseed with annual or perennial ryegrass. Ryegrass is a cool-season grass that will stay green throughout the cool winter months in the south while the warm-season grasses turn brown. That way, homeowners can enjoy a green lawn all winter long. In the spring when the warm weather returns, the warm-season grass will green up, and eventually when the temperatures get warm enough, the ryegrass will die off.
The Transition Zone is an overlap area. Some warm-season grasses do well there due to the hot, dry summers, as do some cool-season grasses, like tall fescue, because of the cold winters. Bermudagrass, centipedegrass, and zoysiagrass are the main warm-season grasses grown in the Transition Zone. They're drought-tolerant and can withstand cooler temperatures better than the other warm-season grasses. However, they often go dormant and turn brown during the winter months when temperatures are consistently below 60°F.