An anti-cyclone brings torrential rain to the southern coastal areas, and extends to the top of the range and into the high plains. However, like today, the rain has a sharp boundary, and while the event can extend a couple of hundred kilometers to the North and South, it is often the case that only the easterly parts of the high plains get the rain. Sometimes the rain events hit with such precision that they bisect a paddock - leaving one side dry and the other under water. The westerly portions, dry and cold, may get little or no rain - but will get the benefit of swollen creeks for months to come.
In the meantime, road travel is restricted and causeways across creeks and rivers are flooded.
These types of rain events can last for a number of days - and if associated with cold off-shore currents, can result in large dumps of snow.
The rain is a good opportunity to wash off the dust from travels.
Edit: I travel through a lot of flooded creeks while travelling through the bush. While this might look fun, it is just a part of ordinary life for anyone living on the other side of creeks, off the main roads.
Sooner or later, you will find yourself with water in front of you. Do not enter it unless you must. Before entering water, check for depth, force and obstructions. Depth can be deceptive - never let a vehicle go into water if the stream is deeper than the distance between the bottom of your car and the ground. Your car will float downstream if the stream is higher - or your car will stall (if the exhaust pipe outlet goes under water).
My 4WD is fairly high but, even so, I will never enter water that does not run entirely under the vehicle (in checking depth, I wind down windows, open the upstream door and enter the water carefully - if water threatens to come in the door, I leave the water). Water force or obstructions might cause the vehicle to loose its footing.
Travelling through water may affect your brakes - you may need to dry them out before needing to use them (this should be a fist priority after getting out of water).
Finally - think twice before doing this for fun. Crossing streams can take a lot out of a vehicle - even a 4WD. Each time I have to do this, I have a list of 20+ points specific to this vehicle I have to check for damage or relubrication.
(Thanks to +Robyn PENGUIN LOVER for reminding me of the risks in crossing flooded streams.)