If it feels hotter than usual, that's because it is.
So far, 2017 is the second hottest year on record, according to the National Oceanic and Atmospheric Administration, and it got so hot in Phoenix last month that airlines couldn’t fly planes.
But which cities will suffer the most?
"It's not always the highest temperatures that get you," explained Radley Horton, a climate scientist at Columbia University who studies extreme heat. "Sometimes, it's the combination of high temperatures and humidity."
Last year, Honeywell Fans and Environmental Health & Engineering found that sweltering Southern cities were the sweatiest in the country.
This year’s list is dominated by big, East Coast cities that typically have cooler temperatures and higher humidity.
- New York
- Washington, D.C.
- New Orleans
Dr. Ted Myatt, who led the Honeywell study, analyzed a number of factors unrelated to weather that might make a city sweat, such as population density.
"We looked at data in a number of national records to determine the percentage of homes without central air conditioning, the popularity of public transportation and citywide bike sharing programs, as well as the cities with the 'hottest' professions," he said in a statement.
New York won the top spot partly because it is home to some of the “hottest” professions per capita — high stress jobs that might make you sweat, including air traffic controller and personal financial adviser.
According to Horton, big cities such as New York can also suffer from the "urban heat island phenomenon." When dark surfaces like asphalt and buildings replace vegetation they trap heat from the sun and raise temperatures in densely populated areas.
Horton predicted that by the end of the century, some cities could see three times more days with temperatures above 90 degrees, and a much higher frequency of longer, hotter heat waves.