Data Release: Our annual analysis of NOAA precipitation data and housing stock statistics reveals a 12% increase in “High Risk” zones across the Southeast.
2025 Key Findings
The National Mold Index has finalized its 2025 aggregated data report. By cross-referencing NOAA annual rainfall totals with US Census Bureau data on housing age (specifically pre-1980 construction), we have identified the regions facing the highest biological threat levels entering 2026.
The trend is clear: “The Wet Bulb Effect.” States with high heat and simultaneous high humidity are seeing a surge in structural mold claims, even in homes without direct flood damage. The ambient humidity alone is enough to sustain colony growth in crawl spaces.
The Top 5 Riskiest States (2025)
The following states achieved the highest composite scores based on our proprietary algorithm (Rainfall + Humidity + Old Housing Stock).
| Rank | State | Risk Score | Primary Factor |
|---|---|---|---|
| #1 | Louisiana | 9.5 / 10 | Extreme Humidity + Flood Zones |
| #2 | Florida | 9.4 / 10 | Atmospheric Moisture |
| #3 | Mississippi | 9.2 / 10 | Aging Housing Infrastructure |
| #4 | Alabama | 8.8 / 10 | Crawl Space Saturation |
| #5 | South Carolina | 8.5 / 10 | Coastal Storm Surges |
The “Surprise” Contenders: The Northeast
While the South dominates the top spots, the Northeast (specifically Rhode Island and Massachusetts) saw the largest year-over-year increase in risk scores.
This is driven by the “Aging Stock Factor.” While these states have less rain than Florida, they have some of the oldest homes in the country. A 100-year-old basement in Rhode Island is far more susceptible to minor water intrusion than a new build in a dry climate.
Methodology Note
The National Mold Index calculates scores using a weighted average:
- 40% Climate Data: Annual precipitation and Average Relative Humidity (Source: NOAA).
- 30% Housing Age: Percentage of homes built before 1980 (Source: Census Bureau).
- 30% Regulatory Environment: State laws regarding landlord disclosure (Source: Legal Analysis).
Where Does Your State Rank?
Access the full dataset. Click our interactive map to see the specific mold score, rainfall average, and housing risk for your location.
View Interactive Risk Map