A so-called "katabatic" wind occurs when cold, therefore dense, air drains down a slope. If the draining air gets squeezed between headlands, the wind generated can be quite sailable. Italy's Lake Garda is an extreme example of this.
I have found that the Clyde River at Bateman's Bay gets a regular katabatic wind. The critical triggers seem to be overnight frosts on the tablelands, and calm conditions at "the Bay".
To take advantage of this phenomenon, you have to be rigged and ready to sail not long after sun up. You can rig big; the wind probably will not exceed 15 knots. The wind will dissipate after about an hour; be prepared to wallow back to shore. The wind will be "offshore", so discretion is required. Early morning is shark feeding time; plenty of incentive to make those gybes!

There are probably lots of places in southern Australia where katabatic winter winds occur. What is "unnatural" is to consider that there's local sailable wind to be had early in the morning, when, so often, the BOM forecast suggests nothing sailable for the entire day.
Good luck in your quest.