This summer has been unrelentingly hot. Humidity is making it feel worse.

Hot, sticky and unrelenting: That has been the experience for much of the country this summer, including more than a dozen states that had record high humidity in July.

Last month was muggier than usual for the majority of the Lower 48. Parts of the Midwest, East Coast and mid-Atlantic regions, in particular, were intensely humid in July, according to preliminary data compiled by researchers at Oregon State University.

Hot and humid conditions are to be expected in the summer, but heat index values — what conditions “feel like” when humidity and air temperatures are combined — soared well into the triple digits for extended periods of time in places such as Ohio, Illinois, Kentucky, Tennessee and Florida last month.

Cities such as Pittsburgh; Roanoke, Virginia; and Washington, D.C., all registered their most humid July in recorded history, according to figures compiled by the Iowa Environmental Mesonet, which collects and tracks data on precipitation, soil temperature and other environmental conditions. New York City and Raleigh, North Carolina, had their second-most-humid July, while humidity in Detroit and Cincinnati reached their third-highest levels last month.

In Paducah, Kentucky, a brutal stretch of high heat and humidity from July 16 to 30 set a slew of new records for the city.

“We have reached the end to the longest stretch of continuously high humidity that Paducah has witnessed in the past 75 years,” the local branch of the National Weather Service said Thursday in a post on X, adding that the number of hours at “oppressive levels” of humidity exceeded 300% of the city’s normal amount for the month of July.

Humid days are expected to be more common as a result of climate change, because a warmer atmosphere can hold more moisture. But beyond the discomfort of a sticky summer, soaring humidity levels pose serious threats to health and public safety.

High heat index values increase the risk of heat-related illness and death, particularly among children, older adults and individuals with pre-existing health conditions. A 2022 study by the nonprofit organization Climate Central found that the combination of high heat and humidity can affect the body’s ability to cool itself down through sweating.

“In many parts of the country and the globe, dangerous heat often occurs along with high humidity — and the pair of conditions multiplies the health risks,” the researchers wrote in their analysis.

A warmer atmosphere can also spawn stronger storms that are capable of dumping huge amounts of rain over land, often causing dangerous flash flooding.

So far this year, more than 3,000 flash flood warnings have been issued by the National Weather Service — the highest number on record, according to data from Iowa State University.

Catastrophic flooding last month killed at least 120 people in central Texas’ Hill Country region, while several rounds of storms inundated parts of New Mexico multiple times in the span of a few weeks in July. On Thursday, right at the end of the month, intense storms pummeled New York City and the surrounding tristate area, wreaking havoc during people’s evening commute.