On Tuesday morning, six days after Hurricane Ian tore through southwestern Florida, Alvaro “Moe” Zuluaga and his team of mold remediators walked through a house in Naples. The walls were cheerfully painted in sunny yellows and palm greens, and beyond a suspiciously musty smell there was little immediate sign that just days before, the entire home had been sitting in a foot of floodwater.

But on closer inspection, the baseboards were swollen. And there was a visible patch of mold in a single shoe.

“If you don’t act right away, the mold will cover everything,” he said.

In 20 years as a mold remediator in South Florida, Zuluaga has seen many houses where people didn’t act, and mold choked the homes from top to floor, settling on clothing and bedding and spreading through ductwork.

The remediators set to work, packing up wet clothes, the gray linen sofa. By the end of the day, they would knock off all the baseboards, pull up the hardwood flooring and cut out the drywall 4 feet from the ground.

Mold may be one of the most devastating, long-term and hidden costs of America’s increasingly humid, wet and stormy climate.

And while the extent of America’s mold problem is difficult to assess, there is consensus that climate change and more intense heat, rainfall and flooding — three key ingredients in a mold outbreak — are heightening the risk. There is relatively little publicly available data around mold rates, although there is robust scientific data that mold poses serious health risks from inhaling spores in the air.

In an acknowledgment of the growing danger, last year the Federal Emergency Management Agency expanded its disaster aid assistance to cover mold growth. Since the start of the program, it has paid out $142.9 million to 95,000 households, and that was before Hurricanes Fiona and Ian struck.

For mold remediation, immediate action is critical. The moment the waters recede or the rains stop, the clock starts. It can take only 24 hours for mold to take root. By the 72-hour mark, it’s too late. Any saturated porous or semiporous surface — a bed, the kitchen cabinets — that hasn’t been treated has to go.

Like many residents of Florida, Zuluaga has seen many hurricanes, and the ghosts of his past storms are “an ever-present memory,” he said. None more so than Hurricane Hugo, the Category 5 storm that in 1989 ripped through several Caribbean islands before making landfall in Charleston, South Carolina. It ultimately cost $11 billion, or $24 billion in today’s currency, making it the costliest hurricane to hit the United States at the time.

Back then, Zuluaga was a high schooler in Puerto Rico. For three weeks, he and his family were without electricity and running water. “I’m lucky to have experienced it,” he said. “It gives me perspective.”

All homes, even the cleanest ones, have fungal or mold spores. They cling to walls, or float around suspended in the air. What separates a healthy home from a remediation-worthy tearout is moisture, which can cause the spores to feed and grow out of control.

There is robust scientific evidence linking mold with respiratory afflictions including wheezing, throat irritation and worsened asthma. Problems are most likely among children, asthma sufferers or people with long-term exposure to high levels of mold, who may become sensitized to the spores.

It’s an open question in academic research as to whether there is a relationship between mold exposure and neurological damage. “It’s difficult to study because a lot of these symptoms are fairly nonspecific,” said Karen Dannemiller, an associate professor at Ohio State University whose lab studies indoor air quality.

Her research has found that spores growing in higher moisture conditions can elicit more of an immune response. Mold “is absolutely a huge issue,” she said.

Climate change is contributing to an uptick in the intensity and range of wet weather events and higher humidity, exposing more people to conditions that introduce moisture into buildings, according to the Centers for Disease Control and Prevention. After Hurricane Katrina, CDC inspectors found that nearly half of the homes they inspected had visible mold growth. Mold is also the most queried subject to the agency’s National Center for Environmental Health.

In hot, humid regions like Florida, there is always the potential for mold growth, even without a hurricane. But during a storm, if moisture enters a building through a broken door, a leaking window frame or a hole in the roof, and then the power goes out and air conditioning stops running, “there’s your formula for massive mold growth,” said Doug Hoffman, the executive director of the National Organization for Remediators and Mold Inspectors, a nonprofit trade group.

Florida adopted some of the nation’s more stringent building codes after Hurricane Andrew, including windows that can withstand hurricane-force winds. But many buildings, particularly old homes in certain areas, weren’t built with modern conditions in mind.

The problem may be worse for low-income individuals and people of color. Studies have shown that they are more likely to reside in poor quality housing, which can increase the likelihood of suffering the effects of mold. On top of that, tenants may also be hesitant to approach a landlord about issues like mold in their housing if they fear eviction, said Dannemiller, who works with the Asthma Express Program, a program that conducts home visits for asthma patients.

Mold remediation can be expensive. And insurance, even if you have it, may not help: Mold damage is not typically covered by standard homeowners’ insurers.

Even if you have an additional mold-specific rider, the coverage for mold damage may be capped. In Florida, the limit is $10,000. And even if you have additional flood insurance, that typically won’t cover mold. (In the Florida counties where residents were told to evacuate, 18.5% of homes had flood insurance coverage.)

In a storm as severe as Ian, the Naples home represents a good case study. The damage to the home was assessed quickly, and the team removed anything that made contact with floodwater. In the next steps, the remediators will sanitize the underlying structure and other surfaces, and the house will be ready for rebuilding.

In a worst-case scenario, however, if a property has been left to sit and the mold has spread through the walls, the house may have to be ripped down to the studs, so that all that is left is a frame.

On Tuesday afternoon Zuluaga and his team went to inspect a 160,000-square-foot furniture showroom and warehouse. The smell was overpowering. During their walk-through, they found that some of the wooden tabletops and ceiling tiles were already showing signs of visible mold. Everything in the warehouse — an estimated $5 million of desks, sofas, lamps — would need to go.

Work from Hurricane Ian alone would tie his team up for the next three years, Zuluaga reckoned. And so, there was no time to waste. Shortly after wrapping up their inspection, he and his team moved on to another home.