As Hurricane Isaias barrels toward the U.S. Gulf Coast as a Category 3 storm, officials are warning residents about the dangers of storm surge, water that accumulates along the shore ahead of and during a hurricane.
"The surge is really what puts people's lives in jeopardy if they haven't heeded evacuation orders," Florida Gov. Ron DeSantis said in a press conference Friday morning. "We always say: You hide from the wind, but you run from the water."
Isaias is expected to make landfall Friday evening along Florida's panhandle.
Storm surge warnings are already in place along the coast, with surges forecast to reach up to 9 feet in some areas.
Storm surge is defined as the "abnormal rise in seawater level during a storm, measured as the height of the water above the normal predicted astronomical tide," according to the National Oceanic and Atmospheric Administration.
According to ABC News chief meteorologist Ginger Zee, when pressure falls in the center of the hurricane, water levels rise, and the water amasses while the storm is still over the open ocean.
As the hurricane nears the shore, strong winds push that amassed water toward the coast. With nowhere left to go, the water moves up and inland.
This can build walls of water -- potentially as tall as 20 feet or more -- which can quickly overpower barriers and flood homes.
If you're inside a coastal home during a storm, the water can approach quickly and viciously, climbing up a home's inside walls.
The risks can be even greater if storm surge combines with high tide, which could quickly create a catastrophic rise in water levels.
While high winds may be thought of by some as the greatest danger in a hurricane, it is actually storm surge that can be the greatest threat to life and property from a storm, according to Zee.
In 2005, during Hurricane Katrina, at least 1,500 people died "directly, or indirectly, as a result of storm surge," according to the National Hurricane Center.
ABC News' Dan Manzo contributed to this report.