This summer, over 70 million Americans have found themselves enduring the muggiest beginning of summer on record, largely attributed to climate change, as detailed by an Associated Press analysis of climate data.
The result has been an uncomfortable and potentially hazardous spike in nighttime temperatures across numerous cities in the Eastern United States.
According to the National Weather Service, many areas across 27 states and Washington, D.C. have faced record-setting days classified as uncomfortable.
These uncomfortable conditions are characterized by average daily dew points of 65 degrees Fahrenheit or higher during June and July, as calculated using information from the Copernicus Climate Service.
The discomfort is further intensified by periods of extreme humidity, where dew points soar to tropical levels for several hours each day.
Cities such as Philadelphia recorded an astonishing 29 days with dew points reaching at least 75 degrees, Washington experienced 27 days, and Baltimore recorded 24 days at similar levels, which are considered oppressive even by standards set in tropical Tampa.
Dew point serves as a vital measure of air moisture and is regarded by meteorologists as an accurate reflection of humidity.
So far this summer, the average dew points for cities including Washington, Baltimore, Pittsburgh, Richmond, Columbus, and St. Louis have surged to levels at least 6 degrees higher than the averages recorded between 1951 and 2020, reflecting an alarming trend in rising humidity.
In fact, data indicates this summer’s average humidity for the entire eastern region of the United States has surpassed 66 degrees, marking the highest level since humidity measurements began in 1950.
Bernadette Woods Placky, chief meteorologist at Climate Central, highlighted, “This has been a very muggy summer. The humid heat has been way up.”
Cameron Lee, a climate scientist and humidity expert at Kent State University, noted that he encountered dew points reaching an extraordinary 82 degrees at his home weather station in Ohio.
This measurement far exceeds the parameters typically used by the weather service to describe humidity.
Lee identified that certain regions in the United States are not only recording higher average humidity levels—especially during the spring and summer months—but are also witnessing a notable increase in extreme humid days.
Long stretches of extremely sticky days are becoming more common, extending across broader geographical areas than before.
High humidity is problematic as it inhibits nighttime cooling, contributing to consecutive nights of record-high low temperatures from the Ohio Valley through the Mid-Atlantic and along coastal states.
According to Zack Taylor, forecast operations chief at the National Weather Service’s Weather Prediction Center, cities such as Raleigh, Charlotte, Nashville, Virginia Beach, and Wilmington, North Carolina, have recorded their hottest overnight low temperatures in history.
New York City, Columbus, Atlanta, Richmond, Knoxville, Tennessee, and Concord, New Hampshire, also came alarmingly close to setting similar records.
Taylor emphasized, “What really impacts the body is that nighttime temperature. 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.”
This phenomenon can take a significant toll on individuals, particularly those lacking access to cooling centers or air conditioning.
The combination of an unusually hot and wet summer with the effects of climate change, driven by burning coal, oil, and natural gas, is evident, as noted by Woods Placky.
Analysis from the Associated Press shows that areas east of the Rockies have observed a mean increase of approximately 2.5 degrees in summer dew points since 1950.
During the mid-to-late 20th century, the eastern half of the country typically experienced average dew points in the low 60s, which were considered noticeable yet manageable.
However, in four out of the last six years, this measurement has reached or exceeded the uncomfortable threshold of 65 degrees.
Lee described the ongoing trend as “huge,” emphasizing that over a relatively short span of time, the data reflects a substantial increase in humidity.
A seemingly modest uptick in average dew points has led to an alarming increase in the frequency of extreme humidity days, which have shifted from occurring merely once a year to several times throughout the summer.
Meteorologists explain that the interaction between higher temperatures and humidity exacerbates the situation: the atmosphere can retain an additional 4% of water vapor for every degree Fahrenheit (or 7% for each degree Celsius) increase in temperature.
Throughout much of the summer, the Midwest and East were subjected to relentless high-pressure systems that intensified temperatures or were inundated with heavy, prolonged rainfall—amounts far exceeding the seasonal average.
Notably missing throughout was the refreshing cool front that occasionally sweeps in to alleviate oppressive heat and humidity.
Fortunately, in August, such a cooling front finally arrived, offering much-needed respite as reported by Taylor.
Regional humidity levels significantly vary across the United States, with the West being considerably drier while the South experiences more occurrences of 65-degree dew points in the summer months compared to the North.
However, this pattern is evolving as highlighted by Marshall Shepherd, a meteorology professor at the University of Georgia, who warned, “Uncomfortable humidity is moving further north.”
He concluded, “Summers now, are not your grandparents’ summers.”
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