There's been lots here about how difficult everyone is finding it.
I'm a typically fair Celt and used to be one of them.
But I got fit about a decade ago and haven't really suffered since. I wouldn't go for a run in the midday sun but can fairly happily carry on with my day/work whatever the weather, whereas before I would be miserable and nights were awful. Now I sleep fine when it's hot.
At work this week, in an old Victorian building with no aircon, people have been complaining that it's intolerable and it's certainly warm but I haven't found it particularly uncomfortable, whereas I've always thought of myself as someone who doesn't like the heat.
Or maybe I've learned to cope better as I've got older, although as I'm perimenopause, that seems unlikely.