The 24 to 48 hour window
The EPA says that if wet materials are dried within 24 to 48 hours, in most cases mold won't grow (EPA). CDPH adds that porous materials wet for more than a day or two may need to come out even before mold is visible (CDPH). That's why the first two days matter so much.
Clean leak vs. floodwater
- Clean water from a supply line or a roof leak can often be dried in place if you act quickly.
- Floodwater from the Russian River, the Laguna, the Petaluma River or a creek is contaminated. So is sewage. The EPA advises calling professionals experienced with contaminated water (EPA). Porous materials it soaked usually need to be removed.
What to do now
- Make sure it's safe to enter: power off to wet areas, no gas smell, structure sound.
- Photograph everything for insurance.
- Remove standing water and move wet belongings out.
- Pull up wet rugs and padding. Open cabinets and closets.
- Run fans and dehumidifiers if power is safe, and ventilate.
- Call a water damage provider for drying (Sonoma County Water Damage) and, if mold appears, a remediation provider.
Our after-the-storm drying and mold timeline walks through each hour and day.
Want a local pro to take a look?It's free for homeowners and there's no obligation.
If mold has already started
Don't paint over it or run a moldy HVAC system. The EPA says not to run HVAC if you suspect it's contaminated, since it can spread mold (EPA). Areas larger than about 10 square feet call for a professional. See mold remediation.
River communities
If you're in Guerneville, Monte Rio, Forestville, Sebastopol or Petaluma, see our local pages: Russian River flood mold, Sebastopol flood mold and Petaluma flood mold.
Where we connect homeowners
- Mold removal in Santa Rosa
- Mold removal in Petaluma
- Mold removal in Rohnert Park & Cotati
- Mold removal in Windsor
- Mold removal in Healdsburg
- Mold removal in Sebastopol
- Mold removal in Sonoma
- Mold removal in Glen Ellen & Kenwood
- Mold removal in Cloverdale
- Mold removal in Guerneville & the lower Russian River
- Mold removal in Forestville
Dealing with this right now?Tell us what's happening and we'll connect you with an independent local provider.
Other services
Sources
- EPA: A Brief Guide to Mold, Moisture and Your Home
- EPA: Mold cleanup in your home
- CDPH: Frequently asked questions about mold
Sources checked October 18, 2026.
Frequently asked questions
Can I save drywall that got wet in a flood?
With contaminated floodwater, usually not. Soaked drywall and insulation are typically cut out above the water line.
How soon will mold appear?
The EPA's 24 to 48 hour drying window is the key benchmark. Growth may not be visible right away, so dry thoroughly and watch for odors.