The CBC webpage doesn't allow comments. My first reaction is "Bull shit". I lived in Miami from the beginning of June 1999 through end of March 2000. I first lived in a hotel, then a temporary apartment for one month, then a regular apartment. The first day in the regular apartment I set the air conditioner to 72°F. But when I returned home from work, I found it frigid! I had to set it to 80°F to be comfortable. Outdoors during the day it often got between 90-100°F.
Weather statistics for Miami says June-August the average daily high is 31-32°C (87.8-89.6°F), average daily low 24-25°C (75.2-77°F). But some days were above 95°F (35°C). And it's just as humid in Miami as any Gulf state. In the summer it often rained just about quitting time; the question was whether rain would stop before it was time to go home. Rain was so hard you couldn't see the next building across the street downtown, it was solid grey. I enjoyed warm sunny days. Often walked to the downtown mall on Saturdays. Went to South Beach occasionally. This article claims humans cannot survive 35°C with high humidity. I did, and enjoyed it.
The article also claims "Over the course of human evolution, Earth hasn't seen that kind of prolonged, oppressive heat and humidity before." Again I have to call Bull Shit. The genus Homo started with Australopithecus, oldest skeletons dated 3 million years ago. There have been several ice ages and several interglacial periods over that time, every 100,000 years. The height of each interglacial period is warmer than today. The last major ice age began 2.6 million years ago, we are in the Holocene interglacial period. If you only count major ice ages, then Australopithecus did live during the last major interglacial, and it was warmer than today. In fact, during a major interglacial, the northern polar ice cap completely melts every summer, the Sahara Desert grows to a maximum larger than today, and Antarctica develops a taiga forest like Alaska, Yukon, or Northwest Territory today. Technically, our planet still isn't fully out of the last ice age because the Greenland, Arctic, and Antarctic ice sheets still exist.
Humans have adapted to live in every environment on this planet. Our ancestors lived in the Siberia during the ice age, with stone tools. Paleontologists found when modern humans migrated out of Africa, they moved to Europe and Siberia. They actually migrated to Siberia at the
beginning of the last minor ice age, which started about 130,000 years ago. When the last minor ice age ended, Siberia became wet, carrots and other plants died out in favour of woody plants and grass, mammoth, woolly rhinoceros, and giant horses died out. Humans probably hunted the last to extinction. Reindeer and caribou thrived, because they eat woody plants. But with big game gone, humans migrated from Siberia to China. I find it amazing they moved
to Siberia at the
beginning of the ice age, and moved out at the end. During that time, humans evolved, they adapted to the climate. And some people wonder why they evolved flat faces, small noses, and eyelids that fold at the eyelash rather than top of eyeball, and fat in the eyelid. That's to keep the eyes warm in Siberia in winter during the ice age.

We also adapted to live in arid areas of Africa. In the Sahel (edge of the Sahara), and right in the Sahara desert itself. Polynesian people spread across islands of the Pacific. All without air conditioning. We'll adapt.