Free Tool · No Signup

Enter your zip. Get your mold risk right now.

Real NOAA humidity for your area. Dew point. A 24-hour rolling trend. A plain-English action plan. No forms between you and the answer.

Live weather data No signup to see the result Free PDF export
The four local factors that drive mold risk: humidity, dew point, wind, and weather station data
Four local signals from NOAA drive every read: humidity, dew point, wind, and the nearest weather station.

Type your 5-digit US zip code.

Fetches real-time forecast data from api.weather.gov (NOAA). Your zip is never stored on our servers.

How it works

1
Type your zip

We convert it to a NOAA grid point. Your zip never leaves your browser.

2
We pull live weather

24 hours of hourly humidity and temperature straight from api.weather.gov.

3
You see the band

Low, moderate, high, or immediate action. Plus the trend chart and next steps.

Heads up: Risk read based on NOAA forecast humidity and Magnus-Tetens dew-point math. Local microclimates (basements, bathrooms, poorly ventilated rooms) can sit 10-20 points above the outdoor average. Not a medical, structural, or legal diagnosis. If you see or smell mold, call a licensed inspector.

FAQ

How is the mold risk calculated?

We pull the next 24 hours of hourly forecast humidity and temperature from api.weather.gov for the NOAA grid point closest to your zip. We average the relative humidity, compute the average dew point with the Magnus-Tetens approximation, and bin the result into Low (under 55 percent), Moderate (55 to 65), High (65 to 75), or Immediate (over 75 percent OR a dew point within 5 F of a typical indoor surface). The same thresholds ASHRAE and the EPA use for indoor air quality.

Where does the data come from?

Zip to latitude and longitude comes from the free Zippopotam.us US database. Weather data comes from api.weather.gov, the National Weather Service public API. Both calls run in your browser. We do not store your zip or your IP anywhere.

What is a safe indoor humidity range?

30 to 50 percent. ASHRAE Standard 55 and the EPA both target this range for comfort and mold prevention. Above 60 percent relative humidity for more than 48 hours, common household mold species (Aspergillus, Cladosporium, Penicillium) start to colonize porous surfaces.

Does this replace a professional mold inspection?

No. This tool gives you an outdoor-climate baseline for your area. Your actual indoor risk depends on ventilation, insulation, plumbing leaks, and specific room conditions. If the tool shows High or Immediate, or you already see stains, odors, or symptoms, book a licensed inspector. Use this tool as an early warning, not as a diagnosis.

More free mold tools

Humidity mold risk calculator

Humidity Mold Risk Calculator

Already have a hygrometer reading? Drop it in. Get a room-specific score in 30 seconds.
HVAC mold inspection checklist

HVAC Mold Inspection Checklist

12-point walkthrough of the spots a pro would check. Branded PDF export.
Storm damage mold timer

Storm Damage Mold Timer

Water event just happened? Track the 24 to 48 hour window in real time.
Post-flood mold risk checklist

Post-Flood Mold Risk Checklist

15 ordered steps after water damage. Photo at every step. Insurance-ready PDF.