How Humidity Impacts Your Indoor Air During Cooler Months in North Florida

When most people think about humidity problems, they picture sticky summer afternoons and an air conditioner that never shuts off. In North Florida, the story is a little different. Even during the cooler months, Tallahassee, Crawfordville, and Wakulla County stay surprisingly humid, and that moisture has a big impact on your comfort, your indoor air quality, and even your health.

This guide explains how winter humidity works in our part of Florida, the signs that your home’s humidity is off, and what you can do to keep your indoor air in a healthy range all season long.

 

What Is “Healthy” Indoor Humidity?

The Environmental Protection Agency recommends keeping indoor humidity between 30 and 50 percent to maintain good indoor air quality and limit biological growth like mold and dust mites. They also note that humidity should stay below 60 percent whenever possible to avoid moisture problems in the home.

Source:
EPA Indoor Air Quality Guidance and EPA Mold & Moisture Guide.

When your home’s humidity is consistently above that range, your air can feel heavy and musty, even when the thermostat says the temperature is comfortable. When it drops too low, your skin, sinuses, and throat start to feel dry and irritated.

Why Winter Humidity Behaves Differently in North Florida

In many parts of the country, winter air is cold and dry. North Florida is different. Our cooler season is shorter and milder, but the air often stays very humid. Historical weather data shows that December in Tallahassee is one of the most humid months of the year, with average relative humidity often in the upper 70s to low 80s even when temperatures feel cool.

Sources:
Florida Climate Center and Tallahassee December Humidity.

Here is what that means inside your home:

• AC runs less, so less moisture is removed. In summer, your air conditioner pulls moisture out while cooling. In winter, reduced run time means humidity removal drops significantly.
• Crawl spaces and slabs stay damp. Moisture stored under or beneath the home rises into the living areas when ventilation slows.
• Warm indoor air meets cooler surfaces. Condensation forms on windows, doors, and ductwork when humid indoor air hits cold surfaces.

This is why homes in the Big Bend area often feel clammy and musty in the winter, even at 65–70 degrees.

 

Signs Your Winter Humidity Is Too High or Too Low

Signs Humidity Is Too High

• Musty odors, especially after damp or cooler days
• Condensation on windows each morning
• Walls or ceilings that feel damp or cool
• Mold or mildew around vents, baseboards, or closets
• Dust buildup faster than normal
• Worsening allergies or asthma
• “Sweaty” ductwork in attics or crawl spaces

Signs Humidity Is Too Low

• Dry throat or nose upon waking
• Static electricity throughout the home
• Dry skin and cracked lips
• Wood floors or trim that shift or creak

North Florida experiences both swings—sticky air during mild weeks and drier indoor air behind cold fronts.

 

How Humidity Impacts Indoor Air Quality and Health

Mold and Dampness

Mold thrives when humidity rises above 60 percent. Drywall, lumber, carpet, and insulation absorb moisture and feed mold growth. Mold spores become airborne and trigger allergy, asthma, and respiratory irritation.

Dust Mites & Allergies

Dust mites thrive in warm, humid environments. According to the American Lung Association, keeping humidity below 50 percent is one of the most effective ways to reduce dust mite populations.

Source:
American Lung Association – Dust Mites.

Viruses & Illness

Extremely humid air encourages mold and bacterial growth; extremely dry air aggravates sinuses and can help viruses stay airborne longer. Maintaining mid-range humidity improves overall respiratory comfort.

 

How Humidity Affects Comfort & Energy Bills

• High humidity makes air feel warmer. Sweat cannot evaporate as easily, making 68 degrees feel muggy.
• Low humidity makes air feel colder. Faster evaporation from skin creates a chill effect, causing homeowners to turn the heat up.

Temperature discomfort in winter is often humidity-related, not thermostat-related.

 

Ductwork, Attics & Crawl Spaces: Hidden Moisture Zones

Homes in Tallahassee and Crawfordville often include:

• Ducts inside unconditioned attics or crawl spaces
• Ventilated crawl spaces that allow outdoor humidity inside
• Slabs that hold moisture after rainfall

When airflow slows during winter, these areas trap moisture. That leads to:

• Condensation on ductwork
• Musty odors pulled through return ducts
• Mold on insulation, joists, or air handler cabinets
• Dust and contaminants leaking into the system

A professional inspection often reveals issues hidden from homeowners. This is also where
air duct cleaning in Tallahassee and
Crawfordville duct cleaning services dramatically improve indoor air quality.

 

How Heat Pumps Affect Winter Humidity

Most homes in North Florida use heat pumps, not furnaces—and they behave differently:

• Heat pumps do not dry air aggressively. Their lower output temperatures maintain humidity rather than reduce it.
• Short run times mean little moisture removal. Mild weather = shorter heating cycles = less humidity control.
• Auxiliary heat may feel drier. But the effect is inconsistent and often brief.

To understand winter heat pump behavior, see:
Why Your Heat Pump Blows Cold Air in Winter.

If your heat pump is short cycling, never quite comfortable, or running constantly, you may benefit from
Trane AC repair in Tallahassee.

 

How to Measure Humidity at Home

A digital hygrometer is an inexpensive tool recommended by IAQ experts. Place one in:

• Main living areas
• Bedrooms
• Near return vents
• Rooms that smell damp or musty

Target 30–50% humidity most of the time. Readings above 55–60% in winter indicate a home moisture problem.

 

Winter Ventilation Mistakes to Avoid

Ventilation helps, but only when conditions outside are favorable. Common mistakes include:

• Opening windows when outdoor humidity is high – this immediately raises indoor moisture levels.
• Skipping exhaust fan use during showers and cooking.
• Running a humidifier “because it’s winter.” North Florida rarely needs added humidity.

Best rule: ventilate only when outdoor air is cooler and drier than indoor air.

 

Common Winter HVAC Odors Related to Humidity

• Musty smell: Mold on coils, ducts, or building materials.
• Dirty sock smell: Bacterial growth on evaporator coils.
• Earthy or damp odor: Crawl space moisture entering the duct system.

Addressing humidity and cleaning the HVAC system typically resolves these odors.

Steps to Keep Winter Humidity Under Control

• Monitor humidity frequently
• Use bathroom and kitchen exhaust fans
• Repair leaks and drainage issues
• Replace filters and clean coils
• Use a dehumidifier in problem zones

 

Frequently Asked Questions About Winter Humidity in North Florida

What should my indoor humidity be in winter?

Aim for 30–50 percent. Anything above 55–60 percent suggests excess moisture buildup.

Should I run a dehumidifier during cooler months?

Yes—many homes in Tallahassee, Wakulla County, and Crawfordville benefit from winter dehumidification, especially in crawl spaces or musty rooms.

Do I need a humidifier in winter?

Rarely. Unlike northern climates, North Florida generally battles high humidity, not dry air. Only use a humidifier during short cold/dry spells.

How do I know if humidity is affecting my health?

Look for symptoms worse at home than elsewhere: sinus irritation, coughing, wheezing, itchy eyes, or recurring congestion—especially when combined with musty odors or visible mold.

Can my HVAC system control humidity?

Partially. Heat pumps help, but shorter winter run times reduce their moisture removal. Many homes need duct sealing, coil cleaning, or whole-home dehumidifiers for proper control.

 

When to Call a Professional

Seek expert help if you notice:

• Humidity above 60% regularly
• Musty odors that keep returning
• Condensation on windows or vents
• Visible mold growth
• Worsening allergies or asthma
• Sweating ductwork in attics or crawl spaces

A qualified HVAC professional can inspect your ducts, evaluate your heat pump, and recommend solutions like sealing, dehumidification, and improved ventilation.

For an indoor air quality evaluation, visit our contact page.

published on Wednesday, December 10th, 2025