Study Reveals: The 150 Moldiest Cities in America

Mold isn’t just an unsightly nuisance in your home – it’s a serious health threat that can trigger everything from breathing problems to severe lung conditions.

But which parts of America face the highest risk? To find out, we analyzed environmental and climate data from multiple research sources* and asked 3,000 homeowners in the USA if they’ve experienced mold in their home over the past year.

The results revealed the 150 U.S. cities where residents are most vulnerable to mold’s dangerous effects.

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Key Findings

The Main Mold Hotspots

It’s no shocker that Florida dominates the list, claiming six of the top ten spots.

Cities like Fort Lauderdale, Orlando, and Tampa are mold magnets, thanks to their tropical climate and constant rainfall.

But what really stands out is how much coastal proximity plays a role.

Many of these cities face relentless humidity year-round, and older buildings often struggle with moisture control.

The South’s Struggle With Moisture

Louisiana and Mississippi are heavy hitters on the moldiest cities list.

From New Orleans to Shreveport, these places deal with a double whammy: flooding risks and swampy surroundings.

Historic architecture in cities like New Orleans also tends to lack the modern ventilation systems needed to combat mold, making these homes a breeding ground for dampness.

Unexpected Locations with Mold

You wouldn’t expect to see Buffalo, New York, or Detroit, Michigan, in a conversation about mold.

But these cities made the list, showing that mold isn’t just a Southern problem.

Older infrastructure in colder climates can trap moisture, especially during snowy winters and wet springs.

This shows that even without tropical heat, mold can find a way to grow.

West Coast Woes

Even the Pacific Northwest, known for its lush greenery, finds itself on the list.

Cities like Seattle and Portland may not face the intense humidity of the South, but their constant drizzle and cool, damp conditions provide plenty of opportunities for mold to grow.

Surprisingly, even California shows up, with Sacramento and Los Angeles making appearances due to poorly ventilated older buildings and pockets of dampness.

Hawaii’s Mold Problem

Hawaii might be paradise, but it’s also a perfect storm for mold.

Cities like Honolulu and Hilo struggle with high humidity and salty    air, which can quickly seep into homes and linger.

Island living comes with its perks, but battling mold is often part of the deal.

Bottom Line

Our study shows how local weather and geography shape mold risk, but it reveals something even more important: the power of smart home maintenance.

In areas where humidity is a constant challenge, simple investments like proper ventilation, routine checks for leaks, and a good dehumidifier can significantly reduce the risk of mold.

*Methodology

Online panel survey of 3,000 respondents based on age, gender, and geography. Internal data sources are used to obtain population data sets. We used a two-step process to ensure representativeness through stratified sampling and post-stratification weighting. Humidity data and influencing environmental factors sourced through Local Climate Offices, Weather.gov, WeatherSpark and University Websites. December 2024.