A 'festering' weather pattern helped make summer 2025 muggy and miserable

USA Today

a day ago

Has this summer been muggier than usual? For nearly two-thirds of the country, the answer is yes.
Tens of millions of Americans in the central and eastern United States have suffered from an extraordinary bout of high humidity, pushing heat indexes into the triple digits and making it harder for people to cool off, especially at night.
The nation's capital and states including Pennsylvania, New York and Ohio recorded some of their highest dew points on record, experts said.
"We've had a much more humid summer than usual," said Owen Shieh, a meteorologist with the National Weather Service's Weather Prediction Center.
The last two months have been relatively mild as far as temperatures, experts said, with fewer heat waves than in recent years. But a lack of cold fronts and stagnant tropical air have helped cause a stifling summer for many.
Part of the problem: A lack of summertime cold fronts that help push out warm, moist air coming from the Gulf and Atlantic, Shieh said.
"These air masses have just been sitting and festering over the East Coast," he said.
More: Late July's oppressive heat forecast isn't normal
With forecasts showing rainy months ahead, the oppressive humidity isn't likely to go away any time soon.
How humid has it been in summer 2025?
Cameron Lee, a climate scientist and associate professor at Kent State University, said parts of the northeastern United States have had some of their highest humidity levels on record.
The dew point for much of the East has been five to seven degrees greater than average, Lee said. The dew point is the measure of how much water vapor is in the air. The higher the temperature, the greater the amount of moisture.
"We're in rarified territory," Lee said.
Another measure of humidity is the overnight minimum temperature. According to Shieh, many major cities throughout the eastern United States, including Baltimore, Washington D.C. and Philadelphia recorded some of their highest overnight temperatures in history.
Why humidity could be dangerous
Extreme heat is the deadliest form of weather, killing over 700 people in the United States each year, according to the Centers for Disease Control and Prevention.
While sweltering daytime temperatures are dangerous, high humidity can make matters worse by blocking your body's ability to cool itself. When you sweat, the atmosphere soaks up the moisture and produces a cooling effect. But when the humidity is elevated, the moisture stays on your body and traps in heat.
"The lack of evaporating moisture leads to that oppressive, sauna feeling," Lee said.
During heat spells, nighttime can bring a reprieve from dangerously high temperatures. High humidity takes away that respite, making it difficult to sleep and generally wearing on the body, he added.
Is climate change increasing humidity?
Along with the stagnant air, experts say climate change is a factor in the higher than average dew points, leading to dayslong bouts when people are contending with rare humidity levels.
"It's the extreme days that are increasing," said Lee, whose research focuses on climate change. "The days when dew points are in the 95th and 99th percentile are becoming more frequent."
Elevated humidity levels expected into the fall season
Looking ahead, Shieh said forecasts show the stifling pattern will likely remain in place for the rest of the summer.
From August through October, the weather service's long range precipitation outlook expects "above average rainfall chances" east of the Mississippi.
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"Rain and humidity go hand-in-hand," he said. "So this trend is most likely to continue from the late summer into the fall."