Weather in July is much the same as California coast in July It is a lot like Hwy 1 San Francisco to Portland as a point of comparison. Lots to see and do but most people would not like it. Much of the scenery is World Heritage caliber and there is at least one official World Heritage site to visit if you are so inclined. Great for hiking and enjoying the local food. Absolutely no big city delights, even in the larger towns -- hence SYD-MEL is one of the busiest air routes in the world (busier than NY-Washington for example).

As for the weather, July can be beautiful (clear sunny skies but cold though generally not freezing) and it can also be torrential rain and big storms that close the coastal route. I've done this drive in winter and enjoyed it, but definitely not for everyone.