I think a lot of the issues are around the humidity levels on top of the heat. One scientist said the humidity levels could soar tomorrow and it may feel like working in a sauna all day. That's the dangerous bit - it causes problems with sweating which is your body's coolant.
And, as many have said, we aren't used to that heat here. Other countries may have air con, break for a long lunch, have shutters at windows (many Mediterranean homes have shutters and/or verandas to shade the windows and provide a place to sit out of the sun - most of our houses don't as we don't need them), people know what to do because it's normal. It's the lack of normality that will catch people out.
And don't forget 300 plus people have already died in Spain due to heat. Yes, that was over a prolonged period - but that's the thing, the prolonged period was not normal for Spain. It's the normality issue that will prove the problem. If we get these temperatures next year, most people will have learned.
Apparently some authorities have snow gritters ready to sand the motorways - because we don't know what will happen to our roads. Our tarmac mix is different to that used in hotter countries because ours has to cope with low temperatures/frost regularly. I remember coming home from secondary school in the 1976 drought, which had the highest temperature of about 36degrees somewhere in the UK, with tarmac melted onto the sole of my shoe. And my area didn't reach 36 degrees then. Again, a longer period of time but a lesser temperature.
And really OP, if you need a hoodie at 24 degrees you must really be unwell - that's t-shirt weather surely. That's a pleasant summer's day here. Or is it just that you're not used to it...like us in the UK with above 30 degree heat.
Maybe it would have been nicer for you to give us some tips as you manage so well in the regular heat. Not involving air con as most of us don't have it. Or swimming pools as we don't have them in every town let alone garden. Or siestas and not being out in the 11-3pm times as our jobs aren't set up like that. Our DS has break at 11am and lunch from 1pm - 1.45pm with over 2000 kids in the school. The school can't adjust much, as they can't stagger lunch and break for two days - it impacts on lessons obviously, the school can't magic up more shade so they'll be fighting for every tree shade and there's no air con in classrooms bar the computing block. Any tips?