Statistically we know that humans who live somewhere that you'll just die in the regular environment due to climate behave very differently from humans who live in a temperate climate like the UK when the actual temperature warrants the same behaviour. If you live in Nunavut or the Iran / Pakistan border you already knew that you can just die from temperature extremes and so you need to ensure you stay at a survivable temperature, in Wales it's quite unexpected.

As a result you actually get many more deaths from extremes in countries where the usual climate is temperate like Britain, even when the actual temperatures aren't as extreme as in countries where that would be more common.