© Stacey MacGregorUluru has so far received 80mm of rain
The surprise soaking is forecast to last at least another five days, gradually shifting from the Kimberley and Northern Territory this weekend, to Queensland and New South Wales next week.
Here's what's going on.
Why is it raining in the dry season?
The cause of the rare winter rains can be traced back to two pools of cold polar air, which earlier this week moved north through WA and caused a dramatic change in the winds blowing over Australia.
These rivers of winds are known as jet streams, which blow about 10 kilometres above the earth's surface and form the boundary between relatively warm and cold air.
There are two jet streams in each hemisphere — a polar and a sub-tropical — and while the polar jet streams often display a wave-like pattern due to advancing cold fronts, the sub-tropical jet stream is normally quite flat.
On any typical winter's day, the sub-tropical jet stream would normally blow from west to east across Central Australia.
However, this week the north-moving cold air shifted it north.
The images below show the comparison between a normal jet stream pattern in winter and the pattern this weekend.
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This shift has caused wind directions to swing a few kilometres above the surface of northern Australia, switching from a dry south-easterly to a moist north-westerly, essentially blowing off the warm oceans near the equator.
The result is a large band of cloud and rain stretching up to 4,000km across the country and will continue through to Wednesday.
How much more rain will fall?
The system has already produced up to 100 millimetres of rain across the Kimberley, which is about 10 times the average for the whole of winter.
More than 50mm has fallen across southern NT, including 80mm at Uluru — about five times its June average.
The cloud band moved further north through Friday, and in just 12 hours Tennant Creek received more rain than it typically receives all winter.
This weekend is likely to bring another 20 to 50mm across the Kimberley and central NT, triggering flood watches and lifting weekly rainfall totals to more than 100mm in some regions.
While rain through Central Australia is not unheard of in winter, it is extremely rare for the tropics, and 50mm in Tennant Creek would be the heaviest rain in winter in 45 years.
By Monday, the cloud band would have shifted east, and is likely to bring between 20 and 50mm across most of Queensland by late Wednesday.
This could come as an unpleasant surprise to holiday-makers from southern states heading north for some winter sun, with modelling indicating isolated pockets of near 100mm on the North Tropical Coast, including around Cairns.
Red centre close to seeing snow
Another impact of the misplaced polar air is near-record cold temperatures for Central Australia.
Alice Springs shivered to a maximum of just nine degrees on Friday, the town's coldest day in nine years.
Even colder weather is likely on Saturday, and at one point this week it even looked like it might snow on the ranges west of Alice Springs.
Maximums are likely to fall as much 10 degrees below average this weekend across the southern and central NT, and are likely to land within one or two degrees off all-time records.
Earlier this week, as the first pulse of polar air was passing over WA, Kalgoorlie recorded its coldest day in more than 60 years, reaching only 8.9 degrees.
Snow for school holidays
Once the rainband finally clears off the east coast on Thursday, the weather map will likely start resembling a more typical winter pattern.
This means cold fronts and showers for southern Australia, and dry weather returning to the north.
For ski resorts, after some rain on Tuesday, a cold front due to arrive on Thursday should produce a healthy top-up of fresh snow.
Year on year in both hemispheres there has been a steady increase of cold air mass and this year is no different. Presently there's a significant amount of cold air rotating around the Southern Pole and it has developed extended arms of cold air that stretch out towards the equator.
These arms of cold air generate strong winds, as in the Jetstream, which meanders its way between the opposing temperature gradients.
Currently the temperature at the tip of one of these arms ( Australia sits between 2 of them ) is - 35c @ 500hpa. The Jetstream that is flowing around said arms is currently -18c, and beyond the Jetstream ( Northern Australia) temperatures are currently -3.5c.
Such differences in temperature gradients causes wind and massively increases the availability of moisture in the atmosphere, hence the unseasonal rains.
I've mentioned it before, cold air is amassing globally, so one should not expect things weather wise to be the same as yester year, for Earth's atmosphere and weather is becoming increasingly volatile.