Warm-season grasses are originally from sub-tropical regions, which is why they thrive in the hot temperatures of the Southern US. The major grasses in this category are Bermudagrass, centipedegrass, St. Augustinegrass, bahiagrass, and zoysiagrass. Bahiagrass grows primarily along the Gulf Coast. Some warm-season grasses are more cold-tolerant than others, which is why zoysiagrass, centipedegrass, and Bermudagrass are often grown in the Upper South, or Transition zone.
Warm-season grasses grow best when temperatures are between 75-90°F, and do most of their growing in the summer.
Many warm-season grasses go dormant and turn brown over the winter, which is why some people overseed with perennial ryegrass. That way, they can enjoy a green lawn all winter long.
The Transition Zone is an overlap area. Some warm-season grasses do well there due to the hot, dry summers, and so do some cool-season grasses because of the cold winters. Tall fescue is more heat- and drought-tolerant than the other cool-season grasses, which makes it a great choice for growing in the Transition Zone. 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 degrees.