Chicago weather is a bit of a local joke. We say if you don't like it, wait fifteen minutes. But honestly, humidity in Chicago today isn't just a punchline—it’s a physical weight you feel the second you step off the Red Line or walk out of an office building in the Loop. It’s that thick, soup-like air that makes a 75-degree day feel like a 90-degree swamp.
You’ve probably noticed it. That weird "glaze" on your skin? That’s not just the heat. It’s the moisture.
When we talk about the humidity in Chicago today, we’re usually looking at the intersection of Lake Michigan’s massive thermal mass and the "lake effect" that fluctuates depending on which way the wind is blowing. If it’s coming off the water, you get a cooling breeze but often a spike in localized moisture. If it’s coming from the south, you’re basically inhaling the Gulf of Mexico. It’s a mess.
What the Dew Point Actually Means for Your Friday
Most people look at the relative humidity percentage on their iPhone weather app and think they understand the vibe. They’re usually wrong. Relative humidity is a bit of a liar because it depends entirely on the temperature. A 90% humidity day in January feels like nothing. A 90% humidity day in July is a health hazard.
You need to look at the dew point.
The dew point is the absolute measure of how much water is actually in the air. In Chicago, when that number hits 65, it’s "sticky." When it hits 70, it’s "uncomfortable." If we’re seeing dew points in the mid-70s today, you’re going to see people visibly struggling on the lakefront path. Your sweat won’t evaporate. That’s the biology of it—evaporative cooling stops working when the air is already full of water. You just stay wet. It’s gross.
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The Lake Michigan Variable
Living in a city that sits on one of the largest bodies of freshwater on the planet changes the game. Lake Michigan acts as a giant heat sink. Today, the water temperature plays a massive role in how that humidity settles into the neighborhoods. Near the Museum Campus or up in Edgewater, you might feel a "lake breeze" that keeps the thermometer lower, but the actual water vapor content remains high.
It’s a microclimate thing.
You can be at O’Hare and feel like you’re in a desert, then drive East on the Kennedy and by the time you hit Ohio Street, the air feels ten pounds heavier. This isn't just your imagination. The National Weather Service (NWS) Chicago office at Romeoville often tracks these "mesoscale" changes where the humidity fluctuates wildly within just five or ten miles.
Why Humidity in Chicago Today Impacts More Than Your Comfort
It’s easy to complain about frizz or sweaty shirts, but the high humidity in Chicago today actually hits the city’s infrastructure. Think about the "L" tracks. Steel expands. The electrical systems on those aging CTA cars have to work overtime to keep the interior cool. When the humidity is high, those AC units drip more, work harder, and fail more often.
Then there’s the health side.
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If you have asthma or COPD, today is a "stay inside" kind of day. Thick air is harder to pull into the lungs. The EPA’s Air Quality Index (AQI) often takes a hit when humidity is high because stagnant, moist air traps pollutants—car exhaust, industrial particulates—closer to the ground. You aren't just breathing water; you’re breathing everything the city hasn’t cleared out yet.
Surviving the "Soup" Without Losing Your Mind
If you’re heading to a Cubs game or just trying to survive a walk through Millennium Park, you have to change your strategy. Cotton is your enemy. It’s a sponge. Once a cotton shirt gets wet with sweat in this humidity, it stays wet for the rest of the afternoon.
Switch to linen. Or those high-tech synthetics that athletes wear.
And for the love of everything, hydrate before you feel thirsty. Because the air is so saturated, your body’s natural cooling mechanism is broken. You’re losing electrolytes even if you don't feel like you're "dripping."
The Science of the Chicago "Steam Bath"
Meteorologists like Tom Skilling (who, let's be real, is a legend for a reason) have spent decades explaining why the Midwest gets these specific bursts of tropical air. It’s called "corn sweat." It sounds fake. It isn't.
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Transpiration from the massive cornfields in Illinois and Iowa releases billions of gallons of water into the atmosphere. This moisture gets picked up by prevailing winds and dumped right on top of Chicago. So, the humidity in Chicago today isn't just Lake Michigan's fault; it's also the fault of every farm within a 300-mile radius. We are literally breathing the breath of corn.
Infrastructure and Energy Costs
When the dew point stays high overnight, the city never gets a chance to "reset." The brick buildings in Lincoln Park and the concrete canyons of the Loop soak up that moisture and heat. This is the "Urban Heat Island" effect. Your ComEd bill is basically a direct reflection of the humidity levels. Air conditioners don't just cool the air; they act as dehumidifiers. They have to pull the water out of the air before they can effectively drop the temperature.
That’s why your AC sounds like it’s struggling today. It’s literally wringing out gallons of water every hour.
What to Actually Do Right Now
Don't just stare at the weather app. If you're planning on being outdoors, check the "RealFeel" or the Heat Index. If the temperature says 82 but the index says 94, trust the 94.
- Seal the windows. If you have a window AC unit, make sure the gaps are stuffed with foam or towels. Humidity leaks in through the tiniest cracks.
- Dehumidifier settings. If you have a basement in an old Chicago bungalow, turn that dehumidifier to 45%. Any higher and you're inviting mold; any lower and you’re just wasting money.
- Hair Care. Look, it’s a losing battle. Anti-frizz serums only go so far when the air is 80% saturated. Just lean into the messy look today.
- Timing. If you need to run on the Lakefront Trail, do it before 7:00 AM. After that, the sun starts "cooking" the lake moisture and the humidity becomes a wall.
The humidity in Chicago today is a reminder that we live in a swamp that decided to become a world-class city. It's frustrating, it's sticky, and it makes the commute a nightmare, but it’s part of the deal. At least it isn't February, right? In six months, we’ll be wishing for this "soup" when the wind chill hits -20.
Final Practical Takeaways
Keep your electrolytes up, especially if you’re working outside. Salt, magnesium, and potassium are your best friends when your sweat isn't evaporating. If you're an apartment dweller, keep the blinds closed on the sunny side of the building. It stops the "greenhouse effect" from making the humidity inside feel even more suffocating.
The humidity will likely break by tomorrow evening when a cold front pushes through from Wisconsin, but until then, just take it slow. Chicagoans are tough, but even the toughest among us can't fight physics.