We see a noteworthy storm before the murder of Caesar. This shows that something tumultuous is about to happen. These are seen as portents from a classical point of view, of which Shakespeare knows. Also we see many things that go against nature - again these are portents that signify that not all is well. So, we see owls in the middle of the day, and lions who walk around Rome casually.
In short, odd things in nature or extreme things in nature are used to show uneasiness.
Try re-reading the text and find evidence on why you think your answer is right even if it takes and hour you will benefit from trying harder than ever and if you ever have to do this again you will be able to do it by your self
