Summer is in full bloom, with heat and humidity relentlessly bearing down and barely easing up when the sun sets. If you are among those thinking it’s hotter than ever, you now have some science to back up your belief. Extreme measures of heat and humidity, some approaching deadly levels, are being recorded more than ever around the world.

Researchers at NASA’s Jet Propulsion Laboratory studied wet-bulb temperatures, a combination of air temperature and humidity, from nearly 8,000 weather stations around the globe from 1979 to 2017. They found the number of extreme measurements has more than doubled since 1979. In some places, the wet-bulb temperature is already at times passing a heat index of 160 degrees, the point at which humans can no longer regulate body heat.

The researchers found periods of extreme heat and humidity occurred repeatedly in India, Bangladesh, Pakistan, northwestern Australia, and along the coasts of the Red Sea and the Gulf of California. The highest readings were spotted 14 times in cities in Saudi Arabia, Qatar and the United Arab Emirates. Southeastern areas of the U.S. experienced extreme conditions dozens of times, mostly near the Gulf Coast in Texas, Louisiana, Mississippi, Alabama and the Florida Panhandle.

More than 30% of the world’s population endures at least 20 days each year above a lethal temperature threshold, a figure that is rising every year. Areas of the planet that are too hot to sustain normal human life are expanding, leading experts to the sobering conclusion that global warming is pushing humanity toward a world that is becoming simply too hot to live in.