Everywhere I've lived I've heard people say, "If you don't like the weather, just wait ten minutes."
None of these people have lived in Melbourne.
So here's the deal:
Pretty much 3-4 days out of every week are about 60F/15C.
In winter the other days of the week are colder.
In summer the other days of the week are warmer.
If you have winds from the south, it means it's going to get colder.
Winds from the north mean it's going to be warmer.
If you wonder if you need an umbrella the answer is yes.
If you wonder if you need a jacket, step outside to check. For me it's usually a yes.