Why Chicagoland Homes Are Struggling With Indoor Humidity in 2026

Every two to seven years, El Niño hits. Warmer-than-normal Pacific Ocean temperatures trigger this weather pattern that brings more rain and extreme storms. It also brings hotter temperatures from June to September, which, when paired with rain, means high humidity.

The World Meteorological Organization (WMO) is predicting an 80% chance of an El Niño starting in June and going to August. If it does hit, WMO predicts a 90% chance it will last through November.

The last El Niño in 2024 saw record-breaking highs across much of the U.S. It also brought Chicago’s hottest summer on record. We’re expecting we’re going to go from winter’s historically low wind chills and late-season snow to heavy downpours and high humidity this summer.

If you’re feeling like it’s impossible to stay comfortable inside, you’re not alone. The extreme weather is making your HVAC system work hard, but that’s just one factor. Air Blue Heating and Cooling‘s guide helps you understand why indoor humidity is a problem and how to keep your home from feeling like a swamp.

Chicago’s Outdoor Humidity and Its Effects Indoors

In the winter, you experience a stack effect. Hot air rises and escapes through a drafty attic or upper-floor windows. As the air flows up and out, cold outdoor air is drawn in on lower floors.

During cold snaps, the outdoor air is already dry. As your furnace runs to heat our rooms and outdoor air comes in, the relative humidity inside your home drops. That’s why you feel static electricity or find your doors stick as the wood frame warps.

As early as May, several days saw daytime highs exceed 80°F at Chicago Midway. June’s temperatures have exceeded 80°F for much of the first two weeks of the month. Rainfall wasn’t abundant in May, but there has been some rain in June. It’s definitely been hot.

Chicago’s temperatures and rain are a small part of the issue. The proximity to Lake Michigan draws humidity from the water and pushes that humid air into lakeside and suburban neighborhoods. This increases the humidity outside your home.

When the outside air is already extremely humid, your HVAC system has to work hard to remove the humidity entering your home. You end up with the opposite problem. Your indoor air feels moist, and it’s uncomfortable.

There’s another issue. The dew point is the temperature at which the air becomes saturated with water vapor. When your indoor climate is humid, cool air hitting a window can trigger condensation if the dew point outside is cooler than the one inside. You now have extra water vapor in your home.

You could turn down the temperature, hoping to feel cooler, but that uses extra energy. There’s a better way to resolve high indoor humidity.

Chicago’s Architecture and Its Impacts on Humidity

Chicago’s homes also pose problems with humidity control. The type of home you have may factor into the best way to keep humidity at the golden zone this summer. Ideally, you want your home’s humidity to fall between 40% and 50% in the summer. More than that increases the risk of mold within your home.

Drafty Older Homes (Pre-1970s)

From the brick single-family bungalows in the South Park Manor District to the Gothic-Romanesque features of the London-style row homes in the Alta Vista Terrace District, older homes are stunning but often drafty.

In the summer, the porous masonry of brick and stone structures allows humidity to enter. Old sill plates also let humid air in, and once that humidity is in the home, it’s hard to get it out.

Making your home airtight by locating drafts and sealing it more effectively is important. A properly sized HVAC system is equally important. Run a dehumidifier in your basement if needed.

Draft-Free Homes (Post-2000s)

Newer homes have vapor barriers and multi-pane windows to eliminate drafts. This also means these homes trap everything. Taking a shower increases indoor humidity, and bathroom fans may not remove it all. The simple act of breathing or cooking dinner adds even more moisture.

That moisture creates condensation on the windows. It increases the risk of mold and mildew on walls, ceilings, or window trim. A properly installed, well-maintained ventilation system is the best way to stop odors, mold, and excessive humidity. A dehumidifier in humid areas, such as a bathroom, also helps.

HVAC Issues That Impact Your Indoor Climate

Problems with your existing heating and cooling system also impact the indoor climate and can lead to high humidity levels. An AC system removes humidity while removing heat from the indoor air.

Fans draw room air into the ducts.
Duct air passes over coils.
Water vapor collects on the evaporator coils.
Water vapor falls into the drain pan and exits the home through a condensate tube.
Several things happen that impact this process.

Oversized AC

When an HVAC installer or DIYer installs an AC system that’s too large for the space, it can cause short cycling. The temperature in the home increases, and the AC turns on. Because it’s too big for the space, it cools the room quickly and turns off again.

An HVAC system cannot remove humidity if it doesn’t run for a long period. Short cycling prevents humidity from being drawn out of the home. You end up with a cold, humid room. It also wears out the components on your HVAC system faster than the average.

Make sure the AC installer you choose uses Manual J calculations to size your AC system. Square footage is a small part of it, but you also have to consider the layout, window sizes and placement, and number of people and pets in the home.

Irregular Maintenance

Having your HVAC system maintained each year ensures it’s running properly. When you have your system cleaned and inspected, you catch potential issues early. Instead of your AC stopping in the middle of the summer, the technician identifies a part that’s starting to wear out and replaces it before it causes a catastrophic failure.

Duct Leaks

Leaky ducts allow warm, moist air drawn from rooms to escape into wall cavities, attics, or basements. Have your ducts inspected every few years and make sure they’re sealed.

It’s also advisable to clean the grates every month to make sure you don’t have hair, fur, or other debris tracked inside, like mowed grass. Change the filter every few months or more often if necessary.

Air Blue Heating and Cooling are experts in resolving high indoor humidity problems. Give us a call or schedule a consultation online to discuss the best solutions to help you avoid feeling damp and soggy this summer while you’re trying to stay cool inside.