Many of the lawns we service in the area are St. Augustine lawns. St. Augustine, unlike other warm season grass types such as Bermuda and Zoysia, only grows via stolons on top of the soil. Each stolon runner will create roots as it grows laterally, but the roots typically only reach a depth of around 6". In comparison, Bermuda can typically create a root zone up to 2' deep allowing for a lot less stress on the plant when mowed low and exposed to the summer heat.
It is not uncommon to see homeowners prefer to cut their St. Augustine at 2" or even lower. However, this exposes the plant to higher levels of stress because a significant portion of the plant is being cut off each week. It also leads to a need for more frequent mowing and exposes the grass to a greater risk of heat stress and disease, particularly brown patch which we see develop mid-to-late summer.
Lowering the height of cut on St. Augustine can be conducive to bringing the grass out of dormancy faster and encouraging a more aggressive growth pattern when needing to fill in areas, but these use cases should be limited.
We maintain our St. Augustine lawns at a height of cut of 3-4" during the growing season to achieve the greatest health and overall quality of your turf grass.