People talk about the weather so often for several reasons. First of all, it is a topic that we all have in common and we can talk about, so if you meet a stranger or if you are introduced to someone, talking about the weather is the perfect way to start a conversation. Secondly, the weather changes every day and it influences practically everyone. The changeable weather is one of the typically British things, that is why they like this topic so much. Thirdly, the weather is a neutral topic that can't offend anybody. Just think about discussing sports or politics...