A pair of large rainbands will sweep across Australia over the coming week, delivering widespread rain to several states.

Two upper-level low pressure systems will pass to the south of Australia next week, helping draw moisture-laden air over the country. This infeed of moisture will occur from both the east and the west, allowing humid air from the Coral Sea and Indian Ocean to move over the country, providing fuel for rainfall.

This weather pattern is expected to cause showers across the southern half of Australia and along the country's east coast this weekend and next week. However, the heaviest falls are expected to occur in Australia’s southeast inland – across the Murray-Darling Basin – where two rainbands could deliver accumulated falls of 50-100 mm over the next seven days.

The first rainband will cross the Murray-Darwin Basin on Monday and Tuesday next week. This will be followed by a second rainband between Wednesday and Friday. While there is some uncertainty regarding where and how much rain these two rainbands will deliver, there is good agreement between forecast models that the rain will affect a broad area of Victoria, New South Wales and southwest Queensland.

Why so much rain in El Niño

The forecast of rain may come as a surprise following last week’s El Niño declaration from the Bureau of Meteorology. El Niño typically causes below average rain in Australia.

One of the reasons Australia is about to see decent rain in El Niño is due to the competing influence of another climate driver: the Southern Annular Mode (SAM).

The SAM is an index that measured the north-south displacement of a belt of westerly winds that flows around Antarctica, passing to the south of Australia. When the SAM is positive in winter, the westerly wind belt shifts further south. This can cause cold fronts and lows to pass to the south of Australia, while allowing high pressure systems to drive moisture-laden winds over Australia from the east.

The SAM is currently very strongly positive, with the index reaching +4.41 on June 24, which is the highest value since May 2023. This positive SAM is helping draw moisture over Australia from the east, which will enhance rainfall from next week’s rainbands.

Does this mean it will be a wet winter?

Despite the coming week’s wet weather, seasonal forecast models are still predicting below-average rain over much of eastern and southeastern Australia this winter due to the influence of a strong El Niño in the tropical Pacific Ocean.

Image: Seasonal rainfall outlook for the July to September period in 2026. Source: Bureau of Meteorology.

So, while this month’s strong positive SAM shows we can still see periods of heavy rain in Australia during El Niño, the outlook is still favouring drier-than-normal weather in the coming months.