The highest storm surge ever recorded in the United States was about 28 feet. Hurricane Katrina produced this extreme surge along the Mississippi coast on August 29, 2005, with a maximum high-water mark of approximately 27.8 feet near Pass Christian.
Katrina’s surge was driven by the hurricane’s enormous size, powerful winds, and approach toward the shallow northern Gulf Coast. Water levels reached roughly 25–28 feet above normal tide along parts of Mississippi, while southeastern Louisiana experienced surges of about 10–20 feet. Waves riding on top of the surge made the flooding even more destructive.
A storm surge is the abnormal rise in seawater caused primarily by a storm’s winds; it is different from the total storm tide, which also includes the astronomical tide. That distinction explains why some reports cite 27.8 feet, 28 feet, or higher flood elevations when wave action is included.
Hurricane Camille previously held the U.S. record with a surge near 24 feet in 1969. Katrina surpassed it, although exact measurements were difficult because gauges and coastal structures were destroyed.