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Portland, Oregon mold guide

Mold Guide for Portland, Oregon

Local mold risk drivers, seasonal priorities, and next steps for homeowners and renters in Portland.

State law data last updated: 2026-02-02

Overview

With 35.9 inches of annual rainfall and an average temperature of 52.5 F, Portland a mix of wet spells experiences and dry breaks.

Statewide weather patterns in Oregon compound local risks, since humidity swings and storm seasons can push indoor moisture above safe levels.

Portland sits in the Willamette Valley, with a long rainy season and cloudy, wet winters that keep materials damp.

Portland Code Enforcement investigates building and property maintenance violations.

This guide highlights local moisture drivers, seasonal risk, and prevention steps. For legal rights and landlord obligations, review the Oregon mold laws guide.

Sources: [Oregon - Climate | Britannica] | [Portland Code Enforcement] | [NOAA Climate Normals - PORTLAND-HILLSBORO AP, OR US]

Action Checklist

Get free access to the full guide

8-step checklist for immediate action

Portland Home Inspection Checklist

Common construction types in Portland affect where moisture problems develop. Here is how local building patterns shape what to inspect.

In Portland, code Enforcement investigates property conditions and code violations.

Documenting moisture damage supports inspection follow up.

Sources: [Portland Code Enforcement]

  • Portland gets roughly 35.9 inches of precipitation per year. Schedule gutter, roof, and drainage inspections seasonally.
  • Roof flashing, gutters, and downspout extensions.
  • Window and door seals exposed to wind driven rain.
  • Crawl spaces and lower level storage areas.
  • Basement walls and floor drains.
  • Bathroom exhaust fans and vent ducts.
  • HVAC condensate drain lines and drip pans.
  • Laundry hoses and shutoff valves.

Sources: [EPA Mold, Moisture, and Your Home] | [NOAA Climate Normals - PORTLAND-HILLSBORO AP, OR US]

Warning Signs of Mold in Portland

Watch for these signs that moisture is lingering in Portland homes and rentals:

  • Persistent window condensation in Portland (annual average 52.5 F) is a common early indicator that indoor humidity is too high.
  • Musty odors after weeks of rain.
  • Condensation on windows that lingers into the day.
  • Peeling paint near window trim.
  • Dark spotting near ceiling corners or closets.
  • Soft drywall around tubs or showers.

Sources: [EPA Mold, Moisture, and Your Home] | [NOAA Climate Normals - PORTLAND-HILLSBORO AP, OR US]

Mold Risk Factors in Portland

These are the most common moisture drivers for homes and rentals in Portland:

  • Climate records show Portland getting 35.9 inches of annual precipitation, so storm events and small leaks both matter.
  • Rainy seasons from fall through spring keep roofs and siding wet.
  • Cool, cloudy winters slow indoor drying.
  • Wind driven rain can penetrate window and door seals.
  • Lower levels and crawl spaces stay damp during long wet stretches.
  • Short dry summers limit exterior drying time.

Sources: [Oregon - Climate | Britannica] | [EPA Mold, Moisture, and Your Home] | [NOAA Climate Normals - PORTLAND-HILLSBORO AP, OR US]

Portland Seasonal Risk Calendar

Fall

Rainy season begins. Inspect roof edges and clean gutters.

Winter

A 52.5 F yearly average means furnaces run heavily. Condensation on cold surfaces is common without consistent airflow.

Spring

Rain continues. Watch basements and crawl spaces for dampness.

Summer

Cool summers still bring rain. Inspect roof edges after storms.

Sources: [Oregon - Climate | Britannica] | [NOAA Climate Normals - PORTLAND-HILLSBORO AP, OR US]

Portland Moisture Playbook

Use this short playbook to stay ahead of common moisture problems in Portland.

After a Leak

Stop the leak, remove wet materials within 24 to 48 hours, and dry with airflow plus a dehumidifier.

Monthly Maintenance

Clear condensate lines, check crawl spaces, and log indoor humidity.

Seasonal Tune Up

Before storm season, clear gutters and inspect flashing; about 35.9 inches of annual precipitation means small leaks can add up.

Sources: [EPA Mold, Moisture, and Your Home] | [NOAA Climate Normals - PORTLAND-HILLSBORO AP, OR US]

Mold Prevention in Portland

Use these priorities to keep indoor humidity low and avoid recurring growth:

  • At 35.9 inches of annual rainfall, maintaining clear gutters and extending downspouts well away from foundations is essential.
  • Maintain indoor humidity between 30 and 50 percent.
  • Dry wet materials within 24 to 48 hours.
  • Vent bathrooms and kitchens outdoors.
  • Clear gutters and direct downspouts away from foundations.
  • Inspect roof flashing and window seals before the rainy season.
  • Service HVAC condensate drains annually.

Sources: [EPA Mold, Moisture, and Your Home] | [NOAA Climate Normals - PORTLAND-HILLSBORO AP, OR US]

Local Regulations

Some cities in Oregon publish additional housing rules or enforcement guidance that can affect mold complaints.

Local regulations are available with the Mold Toolkit

1 city-specific regulations

State Laws and Rights

Oregon mold law snapshot

Oregon does not have a mold-specific statute, but habitability rules still apply.

Oregon law establishes a statutory warranty of habitability under ORS 90.320. A dwelling is considered uninhabitable if it substantially lacks: effective waterproofing and weather protection of roof and exterior walls; plumbing facilities in good working order; adequate water supply capable of producing hot and cold water; adequate heating facilities; electrical lighting with wiring in good working order; buildings and grounds that are safe, clean, sanitary, and free from debris, filth, rubbish, garbage, rodents, and vermin; and safety from fire hazards including working smoke alarms. While mold is not explicitly mentioned, these habitability requirements address the underlying conditions that cause mold growth, and severe mold can render a unit unsafe or unsanitary.

Use the full Oregon guide for tenant rights, landlord responsibilities, and remedies.

Frequently Asked Questions

What are the first signs of mold in a Portland home?
Musty odors, condensation on windows, peeling paint, and dark spots near vents or ceilings are common early signs. If symptoms persist after cleaning, schedule an inspection.
When should I hire a mold professional in Portland?
If the affected area is larger than about 10 square feet, if growth returns after cleaning, or if anyone has health symptoms, hire a pro. Use the DIY vs pro guide to decide.
Are coastal homes in Portland more prone to mold?
Fog, wind-driven rain, and elevated humidity put coastal homes at higher risk. Focus on ventilation, dehumidification, and exterior maintenance. Check our room-by-room guide.
How does salt air affect mold growth in Portland?
Salt air keeps humidity high and can wear down seals and caulk. Inspect exterior joints and ventilate crawl spaces regularly. See our prevention guide.
What should I do about mold after a Portland storm?
Stop the water source, remove wet materials within 48 hours, and run fans and dehumidifiers. Photograph damage for insurance. See the storm recovery guide.
Does flooding increase mold risk in Portland?
Flooding saturates walls, floors, and insulation. Mold can start within 24 to 48 hours. Dry the space quickly and consider professional help. See our flood cleanup guide.