Parts of outback South Australia which are usually extremely dry have received record October rainfall with a highly unusual weather system.

A cut-off low passing over SA caused persistent rain and thunderstorms during the last 24-36 hours, with falls even exceeding some of last week's readings in flood-affected parts of Victoria.

The low was very slow-moving, and drew on a vast amount of tropical moisture. You can get an idea of how it more or less parked itself in the one area in this three-hour loop from Tuesday afternoon.

To illustrate just how much rain fell, let's focus on the weather station at Woomera, the defence facility in SA's North West Pastoral District:

• In the 24 hours to 9 am Wednesday, Woomera received 74.4 mm.
• It was Woomera's wettest day in 23 years, and by far its wettest October day on record (in 75 years of records), with the old record being just 36.1 mm in 1949.
• Woomera's October monthly average is just 15.3 mm, and it has now received 121.4 mm in total to date for the month, after another unseasonably healthy fall of 33 mm last week.
• Woomera's annual average rainfall is a meagre 181.1 mm, so it has now had roughly 60% of its annual rainfall in just two days this month.
• Numerous nearby locations – or "nearby" by outback standards, as in, within a few hundred km – have also now experienced their wettest October on record, including the rural locality of Tarcoola (where records only stretch back 26 years), as well as the mining town of Roxby Downs (25 years of records).

This weather system is easing today in SA today before tracking east, but it still affecting parts of SA as well as parts of the NSW Lower Western forecast district around Broken Hill.

Port Augusta in SA saw 14.4 mm overnight with further showers this morning. It hasn't yet broken its record for the wettest October, but with more rain forecast for later this week, that's a distinct possibility.

Meanwhile, Adelaide has pretty much ducked this system so far, although a wet weekend looks likely at this stage.