Two years' worth of rain could inundate parts of central Australia this week, bringing a risk of widespread flooding in what is typically the driest part of the country.

A slow-moving low pressure system and associated trough will interact with a constant feed of tropical moisture to cause heavy rain and thunderstorms over parts of central Australia every day this week.

Some of this wet and stormy weather will also extend towards southern and southeastern Australia at times over the coming week, meaning moisture from this system will affect parts of most states and territories. However, the heaviest rain will fall in the middle of the country.

Not your average inland soaking

What’s unusual about this rainfall event is that the low pressure system will remain in roughly the same spot for most of the week. Mid-latitude low pressure systems typically impact an area for one or two days before weakening or moving away. This system, however, will sit over the same area for most of this week, causing an unusually prolonged period of heavy rain and thunderstorms.

Another notable feature of this week’s weather setup will be the huge amounts of moisture available in the atmosphere over central Australia. Precipitable water – a measure of how much moisture is available in the atmosphere to produce rain – is predicted to reach 80 mm at times this week. This is an incredibly high value for central Australia. For comparison, when Brisbane Airport registered a precipitable water value of 73.5 mm during a flooding event in January 2024, it was a new record at the time.

How much rain will fall this week?

There is some disagreement between computer models regarding how much rain will fall this week. At this stage, the heaviest rain is expected to occur over the southern half of the Northern Territory, South Australia, southwest Queensland and western New South Wales. These areas could see 100 to 200 mm of rain, with isolated falls possibly reaching around 400 mm. This includes the Simpson, Strzelecki, Sturt Stony and Tirari deserts, which is a region that typically receives around 100mm of rain in an entire year.

Image: Forecast accumulated rain this week according to the ECMWF-HRES model. Source: Weatherzone.

Flooding likely to be widespread

Central Australia’s generally flat landscape and low average annual rainfall means there are fewer well-established rivers and creeks compared to other wetter and more mountainous areas of the country. As a result, heavy rain often causes widespread flooding that can cut off roads and railway lines and even create new waterways in the landscape. Flooding in central Australia can also last weeks as the landscape takes time to drain.

Some of this week’s rain is likely to fall or flow into South Australia's ephemeral (meaning they only fill after heavy rain) creeks and lakes, including Kati Thanda-Lake Eyre and the Strzelecki Creek Wetland System. These waterways could be transformed by this week’s rain and support fresh flora and fauna growth into autumn.

Moisture spreading south

While the heaviest rain is expected to occur over central Australia this week, the vast inland pool of tropical moisture will also fuel rain and thunderstorms in the country’s south and southeast.

A low pressure trough extending over southeastern Australia in the first half of the week will cause showers and storms over parts of Vic, NSW and the ACT on Tuesday and Wednesday. Some of these thunderstorms could become severe, with potential for heavy rain and flash flooding.

Another low pressure trough will drag moisture towards the south over SA from Friday into the weekend. This system could cause heavy rain and potentially severe thunderstorms over much of SA, including the Adelaide region.

How to stay up to date with this week’s rain and flooding

This is an evolving weather event and forecast details are likely to change throughout the week as new and more reliable computer model guidance becomes available.

For the most accurate information, be sure to check the latest forecasts and warnings in your area and be mindful of road closures and flooding if you are travelling.

The State Emergency Services recommends the following safety measures when flooding is occurring:

Have your emergency kit ready

Check on your neighbours

Be prepared to evacuate if advised by emergency services

Never drive, ride or walk through floodwaters

Don't let children play in or near floodwaters