Exactly. The recent heat deaths I saw were people getting heart attack from jumping into cold river and others mostly from dehydration. All are from outside.

You will not die from sleeping in 30c. What europe will have to get used to is slow down over the mid day when the heat is worst.

Night temperatures over 25°c are extremely dangerous for health if continous, there's no getting around this, just get the damn ACs. In my country, we've always had "siestas", now we have ACs too.

You're describing a siesta, which is from Southern Europe (among other places).