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Overview
At 14.8 inches of yearly rain and an average of 44.6 F, Great Falls experiences infrequent rain but high sensitivity to leaks when storms hit.
Montana climate patterns, from seasonal storms to humidity shifts, interact with local conditions to influence indoor mold risk.
Great Falls sees cold winters and warm summers, so moisture risk shifts from winter condensation to spring snowmelt.
Great Falls Building Safety manages building permits, inspections, and code compliance.
This guide highlights local moisture drivers, seasonal risk, and prevention steps. For legal rights and landlord obligations, review the Montana mold laws guide.
Sources: [Montana | Britannica] | [Great Falls Building Safety] | [NOAA Climate Normals - GREAT FALLS INTL AP, MT US]
Action Checklist
Great Falls Home Inspection Checklist
Common construction types in Great Falls affect where moisture problems develop. Here is how local building patterns shape what to inspect.
In Great Falls, building Safety oversees inspections and code compliance for construction and property conditions.
Documenting moisture problems helps support inspection follow up.
Sources: [Great Falls Building Safety]
- Great Falls gets only 14.8 inches of rain per year, but each storm tests roof flashings and window seals. Inspect promptly.
- Chimney flashing, roof valleys, and gutter flow paths.
- Attic insulation and ventilation near eaves.
- Basement walls, sump pits, and floor drains.
- Window frames and sills with condensation.
- Bathroom exhaust fans and vent ducts.
- Water heater pans and HVAC condensate lines.
- Laundry hoses and shutoff valves.
Sources: [EPA Mold, Moisture, and Your Home] | [NOAA Climate Normals - GREAT FALLS INTL AP, MT US]
Warning Signs of Mold in Great Falls
Watch for these signs that moisture is lingering in Great Falls homes and rentals:
- In Great Falls, condensation on cold windows during long heating months (annual average about 44.6 F) is an early moisture signal.
- Condensation that returns on windows each morning.
- Musty odors in basements or closets.
- Peeling paint near baseboards.
- Dark spotting near ceiling corners.
- Soft drywall around tubs or showers.
Sources: [EPA Mold, Moisture, and Your Home] | [NOAA Climate Normals - GREAT FALLS INTL AP, MT US]
Mold Risk Factors in Great Falls
These are the most common moisture drivers for homes and rentals in Great Falls:
- At 14.8 inches of yearly rain, Great Falls homes face more mold risk from HVAC condensation and plumbing leaks than from outdoor precipitation.
- Freeze thaw cycles stress roof flashing and exterior joints.
- Snowmelt and ice dams can leak at roof edges.
- Spring rain can keep basements damp.
- Condensation forms on windows during cold snaps.
- Plumbing leaks behind fixtures can keep wall cavities wet.
Sources: [Montana | Britannica] | [EPA Mold, Moisture, and Your Home] | [NOAA Climate Normals - GREAT FALLS INTL AP, MT US]
Great Falls Seasonal Risk Calendar
Winter
Extended heating with an average of 44.6 F creates condensation risk on cold windows and walls. Maintain steady ventilation.
Spring
Snowmelt and rain keep basements damp. Check sump pumps.
Summer
Cool summers still bring rain. Inspect roof edges after storms.
Fall
Early freezes test roof edges and window seals.
Sources: [Montana | Britannica] | [NOAA Climate Normals - GREAT FALLS INTL AP, MT US]
Great Falls Moisture Playbook
Use this short playbook to stay ahead of common moisture problems in Great Falls.
After a Leak
Stop the leak, remove wet materials within 24 to 48 hours, and dry the area with airflow.
Monthly Maintenance
Check under sinks, clear condensate lines, and log basement humidity.
Seasonal Tune Up
Pre-storm prep matters with 14.8 inches of annual rain. Seal gaps, clear drains, and be ready to dry out quickly after any rainfall.
Sources: [EPA Mold, Moisture, and Your Home] | [NOAA Climate Normals - GREAT FALLS INTL AP, MT US]
Mold Prevention in Great Falls
Use these priorities to keep indoor humidity low and avoid recurring growth:
- Despite only 14.8 inches of annual rainfall, seal window and door gaps before storms to prevent water intrusion.
- 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 storm seasons.
- Service HVAC condensate drains annually.
Sources: [EPA Mold, Moisture, and Your Home] | [NOAA Climate Normals - GREAT FALLS INTL AP, MT US]
State Laws and Rights
Montana mold law snapshot
Montana has mold-specific rules in addition to general habitability standards.
Montana has a strong implied warranty of habitability under the Residential Landlord and Tenant Act of 1977 (MCA 70-24-303). Landlords must comply with all applicable building and housing codes materially affecting health and safety, make all necessary repairs to keep the property fit and habitable, maintain electrical, plumbing, sanitary, heating, ventilating, air-conditioning, and kitchen facilities in safe working condition, keep common areas clean and safe, provide waste disposal, and supply running water and hot water at all times. Landlords must also supply reasonable heat from October 1 through May 1, and must install and maintain smoke and carbon monoxide detectors.
Use the full Montana guide for tenant rights, landlord responsibilities, and remedies.