Courtesy Bureau of Meteorology
For those of us on the east coast of Australia, all that rain is coming from the low pressure system you can see there. But what is really interesting is the cloud over North Australia. If you view a looped image you'll see all that cloud is being sucked from the tropics towards the South East by the low.
Williamtown had 40mm of rain last night. That's the record for June (as mentioned in a previous post).