What's a cause of death? Everyone dies of something... usually more than one thing. AIUI, they've basically put a bunch of factors in to create a regression mo

What's a cause of death? Everyone dies of something... usually more than one thing. AIUI, they've basically put a bunch of factors in to create a regression model which outputs "number of deaths in this area on this day", and the factors for "very hot day or very cold day" are multiplied by the actual number of total deaths to get the "5 million" figure.