When the temperatures drop to freezing your St. Augustine grass will become brown due to being a warm-weather Gainesville lawn. This is normal in your Gainesville landscape as your grass goes into a dormant state. When the weather warms the soil the roots will begin to grow again and your Gainesville lawn will turn green again.
How do you know if your grass has died from the freezing temperatures? Take a piece of grass with the roots and plant it in a container and set it on your window ceil giving it the appropriate amount of water. If it grows and turns green it is fine. If not, then the dead area should be cleaned out and replaced.
Remember that a lush thick web of grass will choke out weeds. If your yard had bald areas, it is important to fill them with either sod or plugs early spring before the weeds awaken below the soil. Gainesville Landscaping companies such as The Master's Lawn Care offer sodding services for areas over a couple hundred square feet. Also, a good Gainesville lawn care program with fertilization and treatments will help it green up after a rough winter too.