Five-thousand members of the Florida National Guard have been activated to help during Hurricane Ian. Another 2,000 guardsmen from Tennessee, Georgia and North Carolina are also coming to help, Florida Gov. Ron DeSantis said.

Nearly 300 ambulances and support vehicles are being deployed to areas bracing for Ian’s landfall, DeSantis said.

-ABC News’ Alex Faul

In Tampa, where residents are bracing for 10 feet of dangerous storm surge, the Tampa International Airport may shut down parts of its airfield and facilities over the next day or two, airport officials announced.

The airport is in an evacuation zone, but because it’s critical infrastructure, it’s “exempt from the storm evacuation order and will stay open until a closure is necessary,” airport officials said in a statement.

It’s been 101 years since Tampa last had a direct hit from a major hurricane.

Hillsborough County Public Schools in Tampa will be closed Monday through Thursday due to the storm. Instead, some schools will operate as storm shelters, the district said.

In Sarasota County, schools will be closed on Tuesday.

NASA said it will roll the Artemis I rocket off the launch pad and back to the vehicle assembly building on Monday night due to the storm.

“Managers met Monday morning and made the decision based on the latest weather predictions associated with Hurricane Ian, after additional data gathered overnight did not show improving expected conditions for the Kennedy Space Center area,” NASA said in a statement. “The decision allows time for employees to address the needs of their families and protect the integrated rocket and spacecraft system.”

Tropical Storm Ian is marching toward the Gulf Coast of the U.S., a region quite vulnerable to hurricanes.

The underwater geology of the Gulf of Mexico is what makes the Gulf Coast particularly unguarded to the massive influx of seawater, said Michael Brennan, acting deputy director of the National Hurricane Center, according to an article on Inside Science.

The symmetry of the Gulf of Mexico, with its shallow, sloping continental shelf, allows the storm surge to be pushed even higher onto land, Brennan told the outlet.

Because the land around the Gulf Coasts is typically flat, that exacerbates the flooding even more and allows the storm surge to travel farther inland, Brennan said.

"Of all of the hazards of hurricanes --- winds, rain, storm surges –-- surges are what can cause the largest loss of life," Brennan told Inside Science.

The Tampa Bay-St. Petersburg area, one of the regions bracing for Ian, is especially vulnerable to storm surge flooding but has avoided a direct hit from a strong hurricane since 1921.

Editor's Note: This post has been updated to reflect proper attribution to Inside Science.

-ABC News' Max Golembo