You’re standing outside, and the air feels like a soggy wool blanket. Your shirt is sticking to your back, your hair is doing things you didn't give it permission to do, and you’re basically breathing soup. If you had to bet money on which state you were in, you’d probably say Florida. Or maybe Louisiana.
Most people would. But honestly? You’d probably lose that bet.
When we talk about the most humid state in the US, we’re actually caught in a bit of a scientific tug-of-war. There is the "relative humidity" answer, and then there’s the "how much do I want to crawl into a freezer right now" answer. Depending on which data point you look at, the winner changes completely. If you go by the strict percentage of moisture the air can hold, the title goes to a state that’s more famous for glaciers than palm trees: Alaska.
The Alaska Curveball
It sounds like a bad joke. Alaska? The place where people wear parkas?
Yeah, it’s true. According to data from the National Centers for Environmental Information (NCEI), Alaska frequently takes the top spot for average annual relative humidity. We're talking about an average of 77% across the state. Compare that to Florida’s average of about 74%, and the "Sunshine State" starts looking a little dry.
But there’s a massive "but" here.
Relative humidity is a tricky metric because it’s relative to temperature. Cold air is like a small sponge; it doesn't take much water to fill it up. Warm air is like a giant industrial sponge. So, even though Alaska's air is often "full" (giving it a high percentage), the actual amount of water vapor floating around is pretty low.
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In Juneau, for instance, you might see 80% humidity, but it’s 45 degrees out. You aren't sweating. You're just... damp. It’s more about mist and fog than the "air you can wear" feeling of the Deep South.
The Dew Point: The Real "Muggy" Metric
If you want to know which state is the most humid in the way that actually ruins your afternoon, you have to look at the dew point. This is the temperature the air needs to cool down to for water to condense.
Meteorologists like Marshall Shepherd, a former president of the American Meteorological Society, often point out that the dew point is a much better indicator of human discomfort. Once the dew point hits 65, it starts feeling sticky. Once it hits 70? It’s miserable. If it hits 75, you’re basically living in a steam room.
When you rank states by average dew point, the leaderboard looks a lot more familiar:
- Florida: The undisputed heavyweight champ of the dew point. With water on three sides and a tropical climate in the south, the air here stays saturated with actual water vapor nearly year-round.
- Louisiana: Between the Gulf of Mexico and the Mississippi River, this state is a literal swamp in the summer.
- Mississippi: It shares the same Gulf-driven moisture that makes the Southeast so notoriously thick.
- Hawaii: Tropical island life comes with a constant, heavy dose of ocean moisture.
In Florida, the average dew point can hover in the high 60s or low 70s for months. In Alaska, it rarely gets that high. So, while Alaska wins the "math" version of the humidity contest, Florida wins the "I need three showers a day" version.
Why the Deep South is So Sticky
It isn't just one thing making the Southeast the most humid state in the US contender. It’s a perfect storm of geography. You’ve got the Gulf of Mexico, which is basically a giant bowl of warm water. Warm water evaporates much faster than cold water.
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Then you have the "Bermuda High."
This is a high-pressure system that sits over the Atlantic and acts like a giant fan, pumping that warm, wet Gulf air straight up into Florida, Alabama, and Mississippi. It’s a conveyor belt of moisture. This is why cities like New Orleans or Jackson, Mississippi, can feel so suffocating.
There's also something called "corn sweat."
If you live in the Midwest—states like Iowa or Illinois—you might notice the humidity spikes like crazy in July. That’s because corn plants "breathe" out water vapor through a process called evapotranspiration. A single acre of corn can release up to 4,000 gallons of water into the air every single day. In the heart of the Corn Belt, this can push dew points higher than they are in the Florida Keys.
Living with the Humidity
High humidity isn't just about frizzy hair. It’s a genuine health and infrastructure issue. When the air is saturated, your sweat can’t evaporate. Since evaporation is how the human body cools itself, high humidity makes it much easier to overheat.
It also wreaks havoc on houses.
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In the most humid states, mold and mildew are a constant battle. In Florida or Louisiana, homeowners often have to run their AC not just for the cold, but to pull the water out of the air. If you turn your AC off for a week in July in Miami, you might come back to find mushrooms growing on your drywall. Okay, maybe not mushrooms, but definitely a fine layer of green fuzz on your leather shoes.
The Verdict
So, what is the most humid state in the US?
If you’re a scientist looking at a spreadsheet of relative humidity, you’ll say Alaska. The cold air is almost always near its saturation point.
If you’re a traveler trying to figure out where you’ll feel the most uncomfortable, the answer is Florida. The sheer volume of water vapor in the air—measured by the dew point—is higher there than anywhere else in the country.
Actionable Insights for Your Next Trip:
- Check the Dew Point, not the Humidity: Before you pack, look at the dew point on the weather app. Anything over 65 means you’ll want moisture-wicking fabrics.
- Morning vs. Evening: Relative humidity is almost always highest in the morning when it’s coolest. If you’re a runner, you might think you’re beating the heat by going at 6 AM, but you’re actually running through the thickest air of the day.
- Hydration is Different: In high-humidity states, you don’t feel your sweat evaporating, so you might not realize how much fluid you’re losing. Drink water even if you don't feel "parched."
- Dehumidifiers are Key: If you move to a humid state, don't just rely on the AC. A standalone dehumidifier can save your basement and your lungs from mold.
Understanding the difference between the "math" of humidity and the "feel" of humidity changes how you look at a map. Whether you're heading to the misty coasts of Alaska or the swamps of Louisiana, just remember: it's not the heat—it's definitely the water in the air.