Ross Hancock sold his four-bedroom house in Coral Gables, a city of pastel luxury at the edge of Miami, because he was worried that sea-level rise would eventually hurt his property’s value. He and his wife, Darlene, downsized to a small condo on Biscayne Bay, perched atop one of the highest coral ridges in the area. There, he presumed, they would be safer.

Then Hurricane Irma hit. 

The September storm pushed water onshore with such force that it penetrated the seams of Hancock’s building, defeating stormproof windows and damaging a third of the units. It knocked out the elevators, ruined the generator, and flooded the parking lot. Months later the park next door remains strewn with mangled yachts hurled from from the ocean.

Hancock outside and inside his building.

Photographer: Rose Marie Cromwell for Bloomberg

Hancock’s unit was spared, but he’s facing a potential $60,000 bill from the condo association for his share of what insurance won’t cover. Now, four years after leaving Coral Gables, he and his wife want to move again—this time, out of Florida. But more than two months after listing their property, they haven’t found a buyer.

“It’s not the greatest time to be showing it,” Hancock said, noting the damage to the building. Still, Irma convinced him that it doesn’t make sense to wait. “At some point, we won’t be able to sell.”

Decisions by people such as Hancock to sell their homes demonstrate that one of the great mysteries of climate change isn’t scientific but psychological: When will the growing risks associated with rising seas and more severe storms begin to affect home values in otherwise desirable coastal markets?

Nowhere is that question more pressing than South Florida, which has some of the country’s priciest properties—and some of the most vulnerable. A state built on real estate speculation,