Which States Have the Moldiest Homes?

In this new ranking from American Home Shield®, we explore the connection between various environmental factors and indoor mold prevalence. While mold can grow anywhere under the right conditions, some states are more susceptible than others due to their unique climate conditions, including higher humidity levels, warmer temperatures, and frequent rainfall. As homes age, leaks and insufficient ventilation can worsen the problem, making mold remediation a costly and recurring issue for many homeowners.

Table of Contents: 

1. States with the Moldiest Homes 
2. States with the Least Moldy Homes 
3. Cities Searching the Most About Mold in the Home 
4. Be Prepared and Know The Risks
5. Methodology 

Ranking Methodology

To uncover which states face the biggest mold problems, we analyzed several key environmental metrics: average annual rainfall, temperature, relative humidity, and dew point. In addition, we looked at the number of Google searches for mold in the home, which can indicate heightened awareness or concern in different regions. Each of these factors was scored on a 20-point scale, with the total scores weighted to reflect the overall risk of mold growth. 

States With the Highest Risk of Mold

Unsurprisingly, the states in the top three spots are located in the Southeast, a region known for its humid climate. Louisiana, with its frequent rainstorms and sweltering summers, took the number one spot with a score of 79 out of 100. Close behind were Florida and Mississippi, where a combination of high humidity and warm temperatures creates the perfect breeding ground for mold. Alabama, with its similarly hot and humid conditions, rounded out the top four with a score of 71.

Top 10 States with the Moldiest Homes 

1. Louisiana
2. Florida
3. Mississippi
4. Alabama 
5. Rhode Island
6. Delaware 
7. Arkansas and Vermont (tied)
8. Georgia
9. South Carolina
10. Tennessee

While states in the South are typically thought of as mold-prone, some surprising contenders emerged from the Northeast. Rhode Island, for instance, ranked fifth with a score of 70 out of 100. The state’s coastal location, combined with cold, damp winters, makes it particularly susceptible to moisture buildup in homes. Similarly, Delaware and Vermont landed in the top 10, showing that while mold is more common in warmer regions, colder states are not immune.

States With the Lowest Risk of Mold 

On the flip side, the West and Southwest, known for their dry, desert-like climates, consistently rank among the least moldy states. Nevada ranks last for moldy homes with a score of 16 out of 100, making it number one on the list for least moldy. Arizona and Utah followed closely, with Utah tying with Colorado at number three. New Mexico and Montana round out the top five.

Top States With the Least Moldy Homes 

1. Nevada
2. Arizona
3. Utah and Colorado (tied)
4. New Mexico
5. Montana
6. Wyoming, Minnesota, and Idaho (tied)
7. Nebraska and California (tied) 
8. Wisconsin, Oregon, and Michigan (tied) 
9. North Dakota
10. South Dakota and Kansas (tied)

Other states in the Midwest and West also fared well, with Wyoming, Minnesota, Idaho, California, Nebraska, Wisconsin, Oregon, and Michigan making the list of states with the least moldy homes.

Cities Searching the Most About Mold in the Home

It's not just state-level data that reveals mold concerns—urban areas also face challenges, especially in cities with dense populations and varying climates. To uncover where mold is a hot topic, we analyzed more than 6,000 Google search terms related to mold remediation in homes across the top 30 major metropolitan areas. The city with the most mold-related search activity? Baltimore, Maryland. This comes as no surprise, as Baltimore's humid summers and older housing stock create an ideal environment for mold growth.

Cities Most Concerned About Mold in the Home 

1. Baltimore
2. Denver
3. Portland, Ore.
4. Seattle
5. Milwaukee

Mold concerns can pop up just about anywhere, but it's cities in coastal areas or places with changing humidity that really stand out. Residents in these spots are searching for mold solutions more than anyone else.

Be Prepared and Know the Risks

Mold awareness is important no matter where you live, but some regions have more challenges than others. In more humid and damp environments, proactive measures like improved ventilation, regular inspections, and prompt remediation can help mitigate the risk of mold damage. Conversely, in arid regions, the natural climate helps reduce mold growth, though occasional storms or leaks can still cause localized issues.

Understanding the risk factors in your area can help you stay ahead of mold problems and protect the health and safety of your home. Mold can be a costly and frustrating problem for homeowners. Mold often occurs in the midst of ventilation failure like a faulty HVAC system, and American Home Shield offers comprehensive home warranties that cover the repair or replacement of parts of key systems like HVAC and electrical as well as appliances—helping you manage unexpected issues before mold even has a chance to move in with you. Don’t wait for a small problem to turn into a big expense. Explore our customizable plans today and gain peace of mind knowing your home is protected!*

Methodology

To determine our ranking, we compared every state across five key metrics: average rainfall (in inches), average temperature (in Fahrenheit), average relative humidity, average dew point, and Google search data about mold in the home. The rainfall and temperature numbers averages are from a 24-month period from August 2022 through July 2024. The average relative humidity and average dew point numbers are from a 2024 study.

We graded each metric on a 20-point score. To determine an overall score, each state’s weighted average was calculated across all metrics. Hawaii was not included in the analysis due to a lack of data.

To determine the number of Google searches, we analyzed 6,635 Google search terms relating to moldy homes over a 24-month period from August 2022 through July 2024. We looked at the average number of monthly searches and compared it to each state and major city’s population, per 100,000 residents.

Sources: National Centers for Environmental Information, World Population Review, and Google Ads

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