More than 2,000 homes in the cities were out of power on Monday after strong winds tampered with power lines.
Tides up to 8m (26 feet) high were recorded, eroding the shoreline in some areas.
Emergency services said they had had over 700 calls for help since Sunday.
About half a dozen people stranded in floodwaters had been rescued, they added.
Meteorologists have warned that this Australian summer will see the impacts of a La Niña weather pattern, which typically brings more rainfall and tropical cyclones.