Probability?

Find the probability that tomorrow morning will be raining. 

Answer : hello? i'm not a geologist :p HAHA

I had just finished studied probability for two hours non-stop. My mum taught me just now and she said that it was really rugi if I didn't score these topic and got zero mark. And I was not really understand the tree diagram part. For the first time I learned these topic when I was in Add Maths class and the teacher just gave us an example question, showing the really big tree diagram and came a long real answers. I became blanked for a while on how it should plus or multiply with these numbers and so on. I felt that I wanted to cry because these should be easy for me but I just don't know how to solve it. 

Oh well, what I needed was a lot of exercising and do more research on where I always did mistakes ( I really needed MORE preparation to pass for upcoming trial ).