it depends where you live... I live in Japan now. One comment I hear often and see reflected in old TV shows is how different summers are already. 20-25 years ago it would have been considered a hot summer day around 30c.
Now every summer day is 30c+.
Also, a comment I hear often is that people didn't really need air conditioners back then. You definitely cannot get away with living in Tokyo without an air conditioners these days!
Same with Los Angeles. In the 1950s, when my parents were young, you didn't need AC in LA. You just opened a window on the few hot days, and those were like high 70s/low 80s.
By the 1990s, you didn't need AC, but your home/rental was more appealing if it had one, because there were a few hot days a year that were pretty uncomfortable otherwise.
Now, you can't not have it. There are far too many hot days to live without it.
Now every summer day is 30c+.
Also, a comment I hear often is that people didn't really need air conditioners back then. You definitely cannot get away with living in Tokyo without an air conditioners these days!