yes you can discuss the weather to Brits no problem. we talk about the weather because we have weather. Other countries have climates. The spring is spring, the summer is summer. the autumn/fall is the autumn/fall and the winter is winter. Either the winter is hot or cold. Depending in the position on the globe. In the UK for Brits we have sun, snow, rain and every type of weather in one day. Outside my window it is windy and breezy, about 18 degrees centigrade, in ten minutes who knows? it might be 36 centigrade or it might be who knows what.

"How are you?" is a ritual question. Basically, it means "Hello. I acknowledge you." The standard answers are "I'm fine. And you?" or "Not bad. And you?"

Not as an immediate response to the question 'how are you?', as the person is asking how you are, not how the day is, but it can lead to that. For example - 'How are you?' 'I'm fine thanks. You?' 'Good, thanks' 'Great weather today. I always feel good when the sun is shining' Something like that. 'How are you' can be a conversation starter, or just a polite inquiry that ends with 'I'm fine/good'; etc, depending on the situation.

The standard answer is "very well thank you and how are you?" discussing the weather, no.

Hi Sayaka, usually when asked 'how are you' its a personal question to whomever it was asked to. Usual responses you would get would be, I'm good, I'm sad, I'm upset, I'm very well etc. I hope this helps.