I'm not from Europe. I'm from Australia.

ATM I live in temperate rainforest, have spent time in tropical heat up in northern QL.

Until the air gets saturated a lot of ability to cope is a combo of adaptation and conditioning. I wear jeans all year round pretty much and generally don't run into problems as long as I'm drinking water. People less use to heat don't move as much blood to their perpheries, probably don't drink anywhere near enough water, and aren't used to feeling comfortable in wet clothing (from sweat or from wetting yourself down).

I spent some time in Thailand and felt like I had found my people when it was a 30 degree day and I put on a jumper, went outside and saw many others doing the same!