Twice this summer climate scientist and humidity expert Cameron Lee of Kent State University measured dew points of about 82 degrees at his home weather station in Ohio. That’s off the various charts that the weather service uses to describe what dew points feel like.
“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 probably 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.
The area east of the Rockies has on average gained about 2.5 degrees in summer dew point since 1950, the AP analysis of Copernicus data shows. In the 1950s, 1960s, 1970s, 1980s and part of the 1990s, the eastern half of the country had an average dew point in the low 60s, what the weather service calls noticeable but OK. 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.