‘Not your grandparents’ summers’: 70 million east coast Americans just had the muggiest June and July in history

WildemanBy The Associated PressBy Seth BorensteinBy M.K

And that meant uncomfortably warm and potentially dangerous nights in many cities the last several weeks, the National Weather Service said

Parts of 27 states and Washington, D.C., had a record amount of days that meteorologists call uncomfortable — with average daily dew points of 65 degrees Fahrenheit or higher — in June and July, according to data derived from the Copernicus Climate Service

And that’s just the daily average

In much of the East, the mugginess kept rising to near tropical levels for a few humid hours

Philadelphia had 29 days, Washington had 27 days and Baltimore had 24 days where the highest dew point simmered to at least 75 degrees, which even the the weather service office in Tampa calls oppressive, according to weather service data

Dew point is a measure of moisture in the air expressed in degrees that many meteorologists call the most accurate way to describe humidity

Louis, the AP calculations show

The humid heat has been way up,” said Bernadette Woods Placky, chief meteorologist at Climate Central

Twice this summer climate scientist and humidity expert Cameron Lee of Kent State University measured dew points of 82 degrees at his weather station in Ohio

That’s off the various charts that the weather service uses to describe what dew points feel . “There are parts of the United States that are experiencing not only greater average humidity, especially in the spring and summer, but also more extreme humid days,” Lee said

He said super sticky days are now stretching out over more days and more land

High humidity doesn’t allow the air to cool at night as much as it usually does, and the stickiness contributed to multiple nighttime temperature records from the Ohio Valley through the Mid-Atlantic and up and down coastal states, said Zack Taylor, forecast operations chief at the National Weather Service’s Weather Prediction Center

Raleigh, Charlotte, Nashville, Virginia Beach, Va., and Wilmington, N.C., all reached records for the hottest overnight lows

New York City, Columbus, Atlanta, Richmond, Knoxville, Tennessee and Concord, New Hampshire came close, he said. “What really impacts the body is that nighttime temperature,” Taylor said. “So if there’s no cooling at night or if there’s a lack of cooling it doesn’t allow your body to cool off and recover from what was bably a really hot afternoon

And so when you start seeing that over several days, that can really wear out the body, especially of course if you don’t have access to cooling centers or air conditioning.” An extra hot and rainy summer weather pattern is combining with climate change from the burning of coal, oil and natural gas, Woods Placky said

In four of the last six years that number has been near and even over the uncomfortable line of 65. “It’s huge,” Lee said of the 75-year trend. “This is showing a massive increase over a relatively short period of time.” That seemingly small increase in average dew points really means the worst ultra-sticky days that used to happen once a year, now happen several times a summer, which is what affects people, Lee said

Higher humidity and heat on each other

A basic law of physics is that the atmosphere holds an extra 4% more water for every degree Fahrenheit (7% for every degree Celsius) warmer it gets, meteorologists said

For most of the summer, the Midwest and East were stuck under either incredibly hot high pressure systems, which boosted temperatures, or getting heavy and persistent rain in amounts much higher than average, Taylor said

What was mostly missing was the occasional cool front that pushes out the most oppressive heat and humidity

That finally came in August and brought relief, he said

Humidity varies by region

The West is much drier

The South gets more 65-degree dew points in the summer than the North

University of Georgia meteorology fessor Marshall Shepherd said uncomfortable humidity is moving further north, into places where people are less used to it

Summers now, he said, “are not your grandparents’ summers.” ___ Borenstein reported from Washington and Wildeman reported from Hartford, Connecticut. ___ The Associated Press’ climate and environmental coverage receives financial support from multiple private foundations

AP is solely responsible for all content

Find AP’s standards for working with philanthropies, a list of supporters and funded coverage areas at AP.org

Explore this year's list.