Where I live in West London the temp reached 42°C in Summer 2019. 40°C+ weather is diabolical.

Feels like someone is holding a radiator about a foot away from you on full blast in all directions. You end up planning how long it will take you to walk to the next building because walking down the road is just not happening. Heat stroke kicks in very quickly, you have to make sure you are wearing loads of sunscreen, a hat, and have plenty of water. When it's so unbearably hot you realise why people from hot countries wear clothes that cover them. It doesn't matter what you wear you'll still feel like you're about to spontaneously combust but at least wearing stuff that covers you will help prevent a bad sunburn.