Probability is fundamentally a measure of uncertainty, an inherent characteristics of a random event. The probability of raining given a specific day has the same interpretation as the mass of the chair you are sitting on.
With this understanding of uncertainty and forget about frequentist view, we can just apply the rule of conditional probability to the raining problem in a way as we apply Newton's law to mass and weight problem. It is purely a mathematical twister.
The following quote is a typical wrong understanding of probability.
2．实际下雨的1天，外出购物1小时遇雨的概率是多少？
日降雨的基础概率是0.4,小时降雨的基础概率是0.1。
1 0天中4天有雨，共96个小时。
10天共240小时，小时有雨基础概率0.1， 共24小时有雨。只要1天中有1个
小时下雨，这1天就是雨天，因此这下雨的24小时都在下雨的4天里。
10个雨天中真正有雨的小时数是24个小时，因此下雨的日子里的小时有雨基
础概率为：24/96=0.25。