A Harvard study of 44 students has confirmed what each and every one of us who has ever been an adult human has learned: summer heat doesn't help you think.
Half the students lived in a building with air conditioning, and half didn't. They were all asked to take a cognitive assessment test on their phones right after getting up. The students with air conditioning did normally, while the students without air-conditioning, however, had 13.4% worse reaction times and coincidentally performed 13.3% worse on the cognitive tests.
The study was conducted over a 12-day period in the summer of 2016, during which there was a five-day heatwave. What's interesting is the heat continued inside long after the outside heat left. Since many buildings are built to retain heat during the winter, they have a tendency to keep all heat in, meaning that a non-airconditioned building can keep the heatwave going inside for sometimes up to 48 hours after the initial natural one. As someone that lived in a crappy Brooklyn building for a particularly brutal summer, I can attest to it getting up to 87ºF inside at night if you forgot to set the timer on the thermostat.
The study has socioeconomic findings, too: if you're too poor to afford air-conditioning you might fall behind at work or at school. In fact, studies are proving this repeatedly.
America, by and large, has an obsession with A/C... 87% of American homes have A/C. There are currently 1.6 billion A/C units in the world, and that figure is expected to be five times greater by 2050 as climate change takes its toll.