Coolest summers of 21st century could be hotter than hottest summers of 20th century

Here in Southern Ontario, we've been having a heat wave (as has been most of North America). Yesterday it was 48°C (118°F). It's been in the 40s for the last couple of days. It's starting to cool off a little bit today, but it's still 37°C (98°F).
It got me thinking about an article I read a while ago: Coolest Summers By Mid-Century Could Be Hotter Than Hottest Of 20th Century. I have asthma, so when the temperatures get up into the high 30s with lots of humidity, I feel like I can't breathe, and like I'm going to pass out. I can't imagine having to endure 48° temperatures without air conditioning. It's the only thing that has made this heat bearable. I'm sure I would have either ended up in the hospital or dead if it weren't for air conditioning.
If summers like this become the norm, and a heat wave is when the temperatures get up into the mid 50s, I don't think I'd be able to survive it.