This ranking identifies ZIP codes nationwide with the highest and lowest mold risk. Mold growth depends on moisture, which is influenced by climate, housing conditions, and water infrastructure reliability. Mold exposure causes respiratory illness, allergic reactions, and property damage.
41,716 ZIP codes analyzed · Worst score: 95/100
25 Worst ZIP Codes
| # | ZIP Code | City | State | Mold Score | Level | Avg Humidity |
|---|---|---|---|---|---|---|
| 1 | 99734 | Prudhoe Bay | AK | 95/100 | very_high | 84.8% |
| 7 | 96939 | — | — | 92/100 | very_high | 82.2% |
| 8 | 96940 | — | — | 92/100 | very_high | 82.2% |
| 9 | 96942 | — | — | 92/100 | very_high | 81.7% |
| 10 | 96943 | — | — | 92/100 | very_high | 82.2% |
| 11 | 96951 | — | — | 92/100 | very_high | 81.8% |
| 12 | 96952 | — | — | 92/100 | very_high | 81.8% |
| 2 | 96010 | Big Bar | CA | 91/100 | very_high | 84.5% |
| 3 | 98539 | Doty | WA | 90/100 | very_high | 78.5% |
25 Best ZIP Codes
| # | ZIP Code | City | State | Mold Score | Level | Avg Humidity |
|---|---|---|---|---|---|---|
| 9 | 95314 | — | — | 0/100 | very_low | 42.8% |
| 1 | 93524 | Edwards | CA | 0/100 | very_low | 38% |
Rankings by State
| State | ZIP Codes |
|---|---|
| Texas | 2,649 |
| California | 2,630 |
| New York | 2,185 |
| Pennsylvania | 2,184 |
| Illinois | 1,583 |
| Florida | 1,484 |
| Ohio | 1,435 |
| Virginia | 1,228 |
| Michigan | 1,167 |
| Missouri | 1,161 |
| North Carolina | 1,085 |
| Iowa | 1,058 |
| Minnesota | 1,009 |
| Indiana | 980 |
| Georgia | 964 |
| Kentucky | 947 |
| Wisconsin | 898 |
| West Virginia | 855 |
| Alabama | 819 |
| Tennessee | 787 |
| Oklahoma | 771 |
| Kansas | 749 |
| Washington | 726 |
| New Jersey | 726 |
| Louisiana | 723 |
Methodology
Mold risk scores combine four factors: average relative humidity (annual and seasonal), housing vintage (pre-1980 construction), FEMA flood insurance claim history, and water system infrastructure violations. Higher scores indicate greater mold risk. Data sources: NOAA humidity data, FEMA NFIP, American Community Survey, EPA SDWIS.
Last updated: 2026-10-20.
Frequently Asked Questions
How are these rankings calculated?
Rankings are based on federal agency data including EPA, FEMA, USGS, and PHMSA. Each ZIP code receives a score based on the specific risk factors for this category. See the methodology section above for details.
How often are rankings updated?
Rankings are regenerated quarterly using the latest available data. The date shown reflects the most recent update.
Explore More 2026 Rankings
- Lead Risk Rankings 2026
- Infrastructure Risk Rankings 2026
- Wildfire Risk Rankings 2026
- Flood Claim History Rankings 2026
- PFAS Contamination Rankings 2026
- School Safety Rankings 2026
- Earthquake Risk Rankings 2026
- CO & Gas Safety Rankings 2026
- Superfund Risk Rankings 2026
- Air Quality Rankings 2026
- Home Safety Rankings 2026