How Heavy Rain Affects Indoor Humidity in Tucson Homes

Heavy rain can increase indoor humidity in Tucson homes by raising outdoor moisture levels, allowing humid air to enter through openings, and introducing water through leaks or damp building materials. Even when rain brings cooler temperatures, your home may feel sticky, damp, or uncomfortable because humidity affects how the air feels. Proper ventilation, moisture control, and air conditioning maintenance can help keep indoor conditions comfortable after a storm.

Tucson is known for its dry desert climate, but significant rainfall can temporarily change the amount of moisture in the air. These changes are not limited to the summer monsoon season. Heavy rain during fall, winter, or spring can also influence indoor comfort, particularly when homes experience poor ventilation, water intrusion, or changes in heating and cooling operation.

Top Care Air provides HVAC diagnostics, maintenance, and repair services throughout Tucson and surrounding Southern Arizona communities. Understanding how rainy weather affects indoor humidity can help homeowners recognize normal changes in comfort, prevent moisture-related problems, and identify when their HVAC system may need attention.

Why Does Humidity Increase When It Rains in Tucson?

Humidity describes the amount of water vapor in the air. When rain moves through Tucson, the surrounding atmosphere often contains more moisture than it does during the region’s typically dry conditions.

Rainfall also wets soil, pavement, landscaping, and building surfaces. As water evaporates, it adds moisture to the surrounding air. Depending on temperature, wind, and ventilation, some of that moisture may enter homes.

Several conditions can contribute to higher humidity during rainy weather:

• Moisture-rich air associated with the weather system.
• Evaporation from wet ground and outdoor surfaces.
• Humid outdoor air entering through doors and windows.
• Air leakage around building materials and openings.
• Rainwater entering through roof or window leaks.
• Reduced air conditioning operation during cooler weather.
• Moisture from everyday indoor activities.

Although outdoor humidity often rises during rainfall, indoor humidity does not always increase by the same amount. A home’s construction, ventilation, indoor temperature, and HVAC operation all influence how much moisture remains inside.

Why Tucson Homes Feel Different After Heavy Rain

Residents of Tucson are accustomed to relatively dry air for much of the year. When outdoor moisture increases, the difference can be noticeable even if indoor temperatures remain comfortable.

A home that normally feels pleasant at 74 degrees may suddenly feel slightly sticky or clammy after heavy rainfall. This does not necessarily mean the thermostat or air conditioner is malfunctioning.

Humidity influences how effectively perspiration evaporates from your skin. When the air contains more moisture, evaporation can become less effective, especially at warmer indoor temperatures.

Common comfort changes include:

• Rooms feeling warmer than the thermostat suggests.
• A sticky or clammy feeling indoors.
• Bedding and fabrics feeling less dry.
• Bathrooms taking longer to dry.
• Condensation appearing on cool surfaces.
• Musty odors becoming more noticeable.
• Uneven comfort between rooms.

Some of these changes are temporary and resolve as the weather dries out. Others may indicate that moisture is entering the home or that the HVAC system is not managing indoor conditions effectively.

How Heavy Rain Allows Moisture Into Your Home

Rain does not need to enter through an obvious leak to affect indoor humidity. Outdoor air can move through small openings around doors, windows, attic penetrations, and other parts of a home’s exterior.

When the outdoor air contains more water vapor than the indoor air, uncontrolled air exchange can introduce additional moisture.

Common entry points include:

• Gaps around exterior doors.
• Worn weatherstripping.
• Window frames and seals.
• Attic access openings.
• Wall penetrations for utilities.
• Improperly sealed ductwork in unconditioned spaces.
• Damaged exterior building materials.

Homes with significant air leakage may experience greater indoor humidity changes during rainy weather.

Improving air sealing can help reduce uncontrolled moisture entry, but homes also need appropriate ventilation to maintain indoor air quality.

Can Indoor Humidity Rise Without a Roof Leak?

Yes. Indoor humidity can increase after heavy rain even when the roof, walls, and windows are not leaking.

Moist outdoor air can enter through normal ventilation and building leakage. Everyday activities such as cooking, showering, and laundry also continue adding water vapor indoors.

During dry weather, this additional moisture may be less noticeable. When outdoor humidity increases, the combined effect can become more apparent.

However, a sudden and persistent increase in humidity should not automatically be attributed to the weather.

Water stains, damp drywall, wet flooring, or recurring musty odors may indicate moisture intrusion that requires further investigation.

How Rain Changes the Way Your Air Conditioner Operates

Your air conditioner does more than lower the temperature inside your home. During cooling operation, it also removes some moisture from indoor air.

Warm indoor air passes over the cold evaporator coil. When the coil surface is below the air’s dew point, water vapor condenses into liquid water.

That water collects in the system’s drain pan and exits through the condensate drainage system.

During humid conditions, the AC may remove more moisture than it does during very dry weather.

However, heavy rain often brings cooler outdoor temperatures to Tucson. When the temperature drops, your air conditioner may run less frequently.

That creates an important difference: the home may have more moisture in the air at the same time the cooling system has less reason to operate.

Why Your Home Can Feel Humid Even When the AC Is Off

When rainy weather lowers outdoor temperatures, your thermostat may not call for cooling as frequently.

For example, if your thermostat is set to 74 degrees and the indoor temperature is already 73 degrees, the AC may remain off even if indoor humidity is elevated.

A standard thermostat primarily responds to temperature, not humidity.

As a result, moisture can accumulate from outdoor air, showers, cooking, or damp materials without triggering the air conditioner.

This is one reason Tucson homes can feel uncomfortable during cooler rainy weather despite not needing additional cooling.

Lowering the thermostat solely to remove humidity may increase energy consumption and make the house unnecessarily cold. If elevated humidity persists, a technician can help determine whether a dedicated humidity-control solution is appropriate.

What Is a Comfortable Indoor Humidity Level?

For many homes, an indoor relative humidity range of approximately 30% to 50% provides a useful comfort and moisture-management target.

Keeping indoor humidity below 60% is especially important because prolonged elevated moisture can encourage mold growth and other moisture-related problems.

Relative humidity measures how much water vapor is present compared with the amount the air could hold at that temperature.

Because relative humidity depends on temperature, the percentage can change even when the total amount of moisture in the air remains similar.

Use these general guidelines:

• Below 30%: Air may feel unusually dry, depending on individual comfort and conditions.
• 30% to 50%: A useful target range for many homes.
• 50% to 60%: Monitor moisture levels and look for condensation or damp areas.
• Above 60%: Persistent readings may indicate a need for better moisture control.
• Above 70%: Sustained levels deserve prompt attention, particularly when surfaces remain damp.

A brief increase during a rainstorm does not automatically indicate a serious problem. The duration of elevated humidity and the presence of damp materials are important factors.

How to Measure Indoor Humidity After Heavy Rain

A digital hygrometer is one of the simplest ways to measure indoor relative humidity.

These small devices display humidity and often temperature, allowing homeowners to monitor changes throughout the day.

Some smart thermostats also display indoor humidity readings.

For useful measurements:

• Place the hygrometer away from direct sunlight.
• Avoid positioning it immediately beside supply vents.
• Keep it away from showers and cooking steam unless measuring those spaces specifically.
• Allow the device time to adjust to the room.
• Check readings at different times of day.
• Compare measurements before, during, and after rainy weather.
• Monitor whether humidity returns to normal after the storm.

If one room consistently has much higher humidity than the rest of the home, investigate localized moisture sources or ventilation problems.

Monitoring actual humidity is more reliable than judging conditions by how sticky the air feels.

Why Some Rooms Feel More Humid Than Others

Indoor humidity is not always distributed evenly throughout a home.

Bathrooms, laundry rooms, kitchens, and rooms with limited airflow may experience higher humidity than surrounding spaces.

Other rooms may be affected by exterior leaks, poor insulation, or air entering from unconditioned spaces.

Common reasons for room-to-room differences include:

• Limited air circulation.
• Inadequate bathroom ventilation.
• Cooking and laundry moisture.
• Leaky windows or exterior walls.
• Airflow restrictions.
• Duct leakage.
• Moisture entering through damaged building materials.

If a particular room becomes humid after every heavy rain, check for water intrusion and ventilation problems rather than assuming the entire HVAC system is responsible.

An HVAC technician can evaluate airflow and system operation when the problem appears related to heating or cooling performance.

Why Bathrooms Stay Damp Longer During Rainy Weather

Bathrooms generate significant amounts of moisture during showers and baths.

During Tucson’s normally dry weather, damp surfaces may dry relatively quickly. When outdoor humidity increases, drying conditions can change.

Bathroom mirrors, walls, tile, and towels may remain damp longer than usual.

To reduce moisture accumulation:

• Use a properly vented bathroom exhaust fan during showers.
• Continue ventilation afterward as needed.
• Confirm that the exhaust fan vents outdoors.
• Wipe excess water from shower surfaces.
• Hang towels where they can dry.
• Repair leaking faucets or plumbing fixtures.
• Check for persistent moisture around windows and walls.

If bathroom surfaces remain wet for extended periods despite adequate ventilation, investigate possible plumbing or building moisture problems.

Can Heavy Rain Cause Condensation Inside Tucson Homes?

Yes. Condensation can occur when humid air contacts a surface cold enough to bring the nearby air below its dew point.

During rainy weather, condensation may appear on windows, mirrors, cold pipes, or other cool surfaces.

Air conditioning supply registers may also develop condensation when surrounding air is unusually humid and the register surface becomes sufficiently cold.

Possible signs include:

• Water droplets on windows.
• Fogging on glass.
• Dampness around cold air vents.
• Moisture on exposed cold pipes.
• Condensation near poorly insulated surfaces.

Occasional condensation can occur under certain conditions, but recurring water accumulation should be investigated.

Persistent condensation can damage nearby paint, drywall, wood, and other moisture-sensitive materials.

Why Your House Might Smell Musty After Heavy Rain

A musty odor after heavy rainfall may indicate that moisture is accumulating in a part of the home.

Possible sources include damp carpets, wet building materials, poorly ventilated rooms, plumbing problems, or moisture entering through exterior openings.

In some situations, odors become more noticeable when humidity increases because moisture changes how existing contaminants interact with the surrounding environment.

Common areas to inspect include:

• Rooms near exterior walls.
• Window frames.
• Ceilings beneath roof penetrations.
• Carpet near doors and windows.
• Bathrooms and laundry rooms.
• Areas around indoor HVAC equipment.
• Storage spaces with limited ventilation.

A musty smell does not prove that mold is present, but it should not be ignored when accompanied by visible moisture or recurring dampness.

Moisture intrusion requires correcting the source. HVAC maintenance alone cannot repair a roof leak or dry severely water-damaged building materials.

Can High Humidity Lead to Mold Growth?

Persistently elevated moisture can create conditions that support mold growth on suitable materials.

Mold requires moisture, and many common household materials can provide a surface where growth occurs.

Problems are more likely when water remains trapped in drywall, carpeting, insulation, wood, or other materials.

Potential warning signs include:

• Visible spotting on damp surfaces.
• Recurring musty odors.
• Persistent condensation.
• Water stains.
• Soft or deteriorating drywall.
• Moisture beneath flooring.
• Areas that remain wet after rainfall.

Wet materials should be dried promptly, ideally within 24 to 48 hours when practical, to reduce the risk of mold growth.

If significant water damage or suspected mold contamination is present, consult an appropriately qualified water damage restoration or mold remediation professional.

Air conditioning maintenance may help address HVAC-related moisture problems, but it is not a replacement for remediation of contaminated building materials.

Can Your AC Help Lower Indoor Humidity After Rain?

Yes. When a central air conditioner operates in cooling mode, it can remove moisture from indoor air as condensation forms on the evaporator coil.

However, the amount of moisture removed depends on the system’s design, operating conditions, airflow, and runtime.

An air conditioner may remove less moisture than expected when:

• Cooling cycles are very short.
• The equipment is oversized for the home.
• Airflow is not properly adjusted.
• The evaporator coil has performance problems.
• The system is not running because the indoor temperature is already low.
• Moisture enters the home faster than the system can remove it.

Some variable-speed systems offer additional humidity-control capabilities, but not every air conditioner has dedicated dehumidification settings.

If your home consistently feels humid despite normal cooling, a professional can evaluate whether the system is operating as intended.

Why an Oversized AC Can Make Humidity Problems Worse

A larger air conditioner is not automatically better for indoor comfort.

When cooling equipment is oversized, it may lower the indoor temperature rapidly and shut off after a short cycle.

Because moisture removal occurs during cooling operation, repeated short cycles can limit the time available for condensation to form and drain away.

During dry Tucson weather, this issue may not be particularly noticeable.

After heavy rain increases moisture levels, the same system may leave the home feeling clammy despite maintaining the thermostat temperature.

Other causes of short cycling include electrical problems, thermostat issues, and certain equipment malfunctions.

Correct HVAC sizing requires a proper cooling load calculation that considers the home’s insulation, windows, construction, orientation, and other characteristics.

Can a Dirty AC Filter Affect Humidity Control?

A heavily clogged air filter can restrict airflow through the HVAC system.

Restricted airflow may reduce cooling performance and, in some conditions, contribute to evaporator coil freezing.

Although filter replacement alone does not solve every humidity problem, proper airflow is important for normal HVAC operation.

Homeowners should:

• Inspect filters regularly.
• Replace filters according to manufacturer recommendations and actual condition.
• Use a filter compatible with the HVAC system.
• Keep supply and return vents unobstructed.
• Avoid blocking airflow with furniture.
• Schedule service if airflow suddenly becomes weak.

Tucson homes may accumulate substantial dust even outside rainy periods, making regular filter inspections especially useful.

Why Your AC Condensate Drain Matters During Humid Weather

When your air conditioner removes moisture from the air, that water must drain away safely.

The condensate drainage system typically includes a drain pan and piping that carries water away from the indoor equipment.

During more humid weather, an operating AC may produce additional condensate.

If the drain becomes clogged, water can back up and potentially cause damage around the indoor unit.

Signs of a possible drainage problem include:

• Water collecting near the air handler.
• A full or overflowing drain pan.
• Unexpected AC shutdowns.
• Moisture stains near HVAC equipment.
• Recurring drainage problems.
• Unusual moisture around the indoor unit.

Some systems have safety switches that interrupt cooling when condensate drainage fails.

If you notice water leaking from indoor HVAC equipment, schedule professional service rather than allowing the system to continue operating with an unresolved drainage problem.

Should You Open Windows After Heavy Rain in Tucson?

Opening windows can improve ventilation under appropriate outdoor conditions, but it does not always lower indoor humidity.

After heavy rainfall, outdoor air may contain more moisture than indoor air. Opening windows during those conditions can introduce additional humidity.

Whether ventilation helps depends on outdoor temperature, actual moisture content, and indoor conditions.

Consider these factors before opening windows:

• Outdoor humidity and dew point.
• Indoor humidity readings.
• Outdoor temperature.
• Air quality and airborne dust.
• Whether rain is still entering through openings.
• How well the home is ventilated.

Cool outdoor air can sometimes provide useful ventilation, but relative humidity alone does not tell the full story because cooler air holds less water vapor than warmer air.

For better decisions, compare indoor and outdoor moisture conditions rather than assuming that rainy outdoor air is always too humid or always helpful.

Do Ceiling Fans Help With Indoor Humidity?

Ceiling fans and portable fans improve air movement, which can make occupied rooms feel more comfortable.

Air movement helps perspiration evaporate from your skin, creating a cooling sensation.

However, fans do not directly remove water vapor from the air.

They may help certain damp surfaces dry when moisture can be carried away through appropriate ventilation or dehumidification, but circulating air alone does not solve a high-humidity problem.

Use fans as a comfort tool rather than a substitute for moisture control.

If the indoor humidity remains elevated, investigate ventilation, water intrusion, or dehumidification needs.

When Should You Consider a Dehumidifier?

A dehumidifier may be helpful when indoor humidity remains elevated even though the home does not need additional cooling.

This situation can occur during cooler rainy weather when the air conditioner operates infrequently.

Portable dehumidifiers can remove moisture from individual rooms or smaller spaces. Whole-home dehumidification systems may be appropriate for some properties with persistent moisture-control needs.

Consider additional humidity control when:

• Indoor humidity repeatedly stays above 60%.
• Rooms feel damp despite comfortable temperatures.
• Condensation regularly develops on surfaces.
• The AC rarely runs during humid weather.
• Moisture problems continue after leaks have been ruled out.
• Specific rooms have recurring humidity concerns.

Dehumidifiers do not correct active roof leaks, plumbing failures, or major water intrusion.

The moisture source must be addressed before relying on equipment to manage the remaining humidity.

How to Lower Indoor Humidity After Heavy Rain

Managing indoor humidity starts with reducing unnecessary moisture and making sure the home’s ventilation and HVAC systems are working correctly.

These steps can help Tucson homeowners respond to rainy conditions.

1. Measure indoor humidity: Use a hygrometer to determine whether moisture levels are actually elevated.
2. Check for leaks: Inspect accessible areas around windows, doors, ceilings, and plumbing fixtures.
3. Use bathroom ventilation: Run properly vented exhaust fans during and after showers.
4. Control cooking moisture: Use kitchen ventilation that exhausts outdoors when appropriate.
5. Keep windows closed when outdoor air is moisture-laden: Avoid introducing unnecessary humidity.
6. Inspect your AC filter: Replace a dirty filter when needed.
7. Monitor HVAC operation: Pay attention to short cycling, weak airflow, or water leaks.
8. Dry wet materials promptly: Do not allow rainwater to remain trapped in carpets or building materials.
9. Consider dehumidification: Use suitable equipment if moisture remains elevated.
10. Schedule professional service: Have persistent HVAC-related comfort problems evaluated.

A short period of elevated humidity after rainfall may resolve naturally. Persistent or worsening conditions deserve closer attention.

How Tucson’s Desert Climate Makes Rain-Related Humidity Noticeable

Tucson’s normally dry conditions influence what residents consider comfortable.

When a weather system introduces additional atmospheric moisture, the change can feel dramatic compared with the usual desert environment.

Heavy rainfall can occur outside the traditional summer monsoon season, so homeowners should not assume humidity concerns are limited to July, August, or September.

Fall and winter rainstorms can produce an unusual combination of cool temperatures and elevated moisture.

During these periods, the air conditioner may not run much because the home does not require cooling.

Meanwhile, wet landscaping, increased outdoor moisture, and normal household activities may influence indoor humidity.

This combination explains why a Tucson home can feel damp after a cool rainstorm without feeling particularly hot.

Can Heavy Rain Increase Indoor Humidity Even in a Newer Home?

Yes. Newer homes may have better insulation, windows, and air sealing, but indoor humidity still depends on ventilation, moisture generation, and HVAC operation.

A tightly sealed home may experience less uncontrolled outdoor air infiltration, yet moisture generated indoors can accumulate if ventilation is inadequate.

Bathrooms, kitchens, laundry rooms, and household activities continue producing moisture regardless of a home’s age.

New construction can also contain residual moisture from certain building materials, although this is a separate issue from temporary rain-related humidity.

If a newer Tucson home regularly experiences elevated humidity, evaluate ventilation and moisture sources rather than assuming the building’s age rules out a problem.

Does High Humidity Increase Energy Bills?

Elevated indoor humidity can affect energy use when the air conditioning system must operate longer to manage cooling and moisture.

Some homeowners also lower the thermostat because humid air makes them feel warmer.

Lowering the temperature unnecessarily can increase cooling costs without fully addressing the underlying moisture problem.

However, rainy weather may also lower outdoor temperatures and reduce the home’s cooling demand.

As a result, heavy rain does not automatically mean higher electricity bills.

The overall effect depends on outdoor temperature, indoor humidity, system operation, and household behavior.

If energy consumption increases significantly while indoor comfort declines, an HVAC evaluation may help identify performance problems.

When High Humidity May Indicate an HVAC Problem

A temporary increase in humidity during rainy weather does not necessarily indicate that your air conditioner needs repair.

However, certain symptoms suggest that the system may not be operating correctly.

Contact an HVAC professional if you notice:

• Humidity remaining unusually high for extended periods.
• Short cooling cycles that occur repeatedly.
• Weak airflow from supply vents.
• The AC running without maintaining the thermostat setting.
• Water leaking around the indoor unit.
• Ice forming on refrigerant lines or coils.
• Unexpected system shutdowns.
• Unusual noises or odors from HVAC equipment.
• Significant changes in comfort without an obvious explanation.

An HVAC technician can evaluate airflow, cooling performance, condensate drainage, controls, and other system components.

Not every humidity concern requires a repair. In some homes, ventilation, building air leakage, or a separate moisture source may be the primary issue.

How Professional AC Maintenance Helps With Humidity Control

Routine HVAC maintenance supports normal system operation and can help identify conditions that interfere with indoor comfort.

During a maintenance appointment, a technician may inspect components related to cooling and moisture removal.

Depending on the system, this can include:

• Evaluating airflow.
• Inspecting the air filter.
• Checking evaporator coil condition.
• Examining condensate drainage.
• Reviewing thermostat operation.
• Checking electrical components.
• Evaluating cooling performance.
• Identifying abnormal cycling behavior.

Maintenance cannot prevent every humidity problem, especially when moisture enters through leaks or damaged building materials.

However, keeping the HVAC system operating correctly helps ensure that it can perform its intended cooling and moisture-removal functions.

When to Call Top Care Air for Indoor Comfort Problems in Tucson

If your Tucson home remains uncomfortable after heavy rain, start by measuring indoor humidity and checking for visible moisture problems.

If there is no obvious water intrusion but the HVAC system is operating abnormally, a professional inspection can help identify the cause.

Top Care Air provides AC diagnostics, repair, and maintenance services for homeowners throughout Tucson and surrounding Southern Arizona communities.

Professional HVAC service may be helpful when:

• The home feels clammy despite normal thermostat readings.
• The air conditioner cycles on and off unusually quickly.
• Cooling performance has declined.
• The condensate drain is leaking or backing up.
• Airflow is weak or inconsistent.
• Indoor comfort problems continue after the weather improves.

A technician can determine whether the issue involves HVAC operation or whether additional building moisture investigation is appropriate.

Keep Your Tucson Home Comfortable After Heavy Rain

Heavy rainfall can temporarily increase indoor humidity in Tucson by introducing moisture-rich outdoor air, affecting building materials, and changing how often your air conditioner operates. Even when outdoor temperatures become cooler, elevated humidity can make rooms feel sticky or damp. Monitoring indoor humidity, controlling moisture sources, maintaining proper ventilation, and keeping your HVAC system in good condition can help improve comfort after a storm.

Top Care Air offers professional AC maintenance in Tucson, AZ to help homeowners maintain reliable heating and cooling performance. If your home feels unusually humid after heavy rain or your air conditioner is not operating as expected, contact Top Care Air to schedule a system inspection and get help restoring comfortable indoor conditions.

Frequently Asked Questions

Why Is My House So Humid After Heavy Rain in Tucson?

Heavy rain can increase outdoor moisture levels, allowing humid air to enter through ventilation and small building openings. Rainwater leaks, damp materials, and reduced air conditioning operation can also contribute. Measuring indoor humidity can help determine whether the increase is temporary or persistent.

What Should Indoor Humidity Be in a Tucson Home?

For many homes, an indoor relative humidity range of approximately 30% to 50% is a useful target. Persistent levels above 60% may increase the risk of moisture-related problems. The appropriate level can vary based on indoor temperature, building conditions, and individual comfort.

Can Rain Make My House Feel Hotter Even When It Is Cool Outside?

Yes. Higher humidity can make indoor air feel warmer or clammy because moisture affects how efficiently perspiration evaporates from your skin. A home may feel uncomfortable even when the thermostat displays a normal temperature.

Does Running the AC Remove Humidity After Rain?

Air conditioners remove some indoor moisture during cooling operation when water vapor condenses on the evaporator coil. However, if rainy weather lowers indoor temperatures, the AC may not run frequently enough to provide significant dehumidification.

Should I Open My Windows to Lower Humidity After a Rainstorm?

It depends on the outdoor and indoor moisture conditions. Opening windows can introduce additional humidity when outdoor air contains more moisture. Compare indoor and outdoor conditions before ventilating, and avoid allowing rainwater to enter the home.

Can Heavy Rain Cause Mold Inside My Tucson Home?

Heavy rain can contribute to mold problems if water enters the home or materials remain damp. Persistent humidity can also support mold growth under suitable conditions. Address leaks promptly, dry wet materials, and seek qualified remediation assistance when significant contamination is suspected.

Why Does My AC Not Remove Humidity When It Is Raining?

During cooler rainy weather, your AC may not operate frequently because the indoor temperature is already near the thermostat setting. Other possible factors include short cycling, improper equipment sizing, airflow problems, or cooling system malfunctions.

When Should I Schedule AC Service for High Indoor Humidity?

Consider professional HVAC service if indoor humidity remains elevated, cooling performance declines, the AC repeatedly short cycles, or moisture appears around the indoor equipment. A technician can evaluate whether the problem is related to HVAC operation or another moisture source.