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Eastern Australia is experiencing major flooding for the fifth time in 19 months due to record-breaking wet weather that is predicted to stretch into next year.

Across October, heavy downpours have flooded large swathes of New South Wales, Victoria and Tasmania, resulting in four people dying, thousands of people being evacuated, homes and shops being inundated, and roads being cut off and damaged.

In New South Wales, the worst-affected state, , mostly in rural areas, with some floods spanning hundreds of kilometres.

“This really is an emergency of some magnitude.” Deputy Commissioner Daniel Austin says his crews are focusing on large areas across the state today including Moree, Narrabri and Moama.

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To try to limit the damage, over half a million sandbags have been dispatched in recent weeks. “We are quite literally sandbagging the state at present,” said Steph Cooke, emergency services minister for New South Wales, on 22 October.

Echuca. The sandbag wall between floodwater and homes.

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The state was also badly hit by the four other major floods that have affected eastern Australia since early 2021, when the unusually wet conditions began. The widespread damage has made them the .

“By the time we get through this event, we have almost the entire state at some point in time that has been affected by a natural disaster of one form or another,” said New South Wales premier Dominic Perrottet at a press conference on 24 October.

In Sydney, the state’s capital, a record-breaking 2.4 metres of rain has been recorded this year, which means about ’ worth of water has fallen on the city. “We not only broke the record, we annihilated it,” , a meteorologist at national broadcaster ABC, on 22 October.

Several parts of Victoria and Tasmania have also , causing flooding in and .

The 19 months of wet weather has primarily been driven by two large-scale weather systems originating in the oceans on either side of Australia, says at the University of New South Wales in Sydney.

Today NSW SES crews alongside partner agencies provided medical resupply and assisted the inundated community of NSW with flood evacuations.

Currently there are two Emergency Warnings out for parts of North Gunnedah.

? Justin Thomsen NSW SES Dapto Unit

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One is La Niña – a weather system arising in the Pacific Ocean that brings rain to Australia’s east coast. A rare grouping of three La Niña cycles in a row since late 2020 has meant “basically no stop in the wet conditions,” says Ridder.

The other is a weather system called the Indian Ocean Dipole, which occurs in the Indian Ocean and is currently in its negative phase, which brings more rain to south-eastern Australia.

Climate change may also be contributing because every extra 1°C of warming in the atmosphere means it can hold an extra 7 per cent of moisture that can then become rain, says Ridder.

“It will take time to quantify exactly how much human-caused climate change has influenced this specific event,” says at the University of Melbourne.

The reason the past few weeks have been particularly wet is because a high-pressure weather system off Australia’s east coast has stopped rain clouds that have been sitting over the eastern states from moving offshore, says Ridder.

Eastern Australia should start to see drier conditions early next year when La Niña is predicted to end, she says. However, even small amounts of rain beyond that point could still cause more flooding because the ground is so saturated that it has limited capacity to soak up any more water, she says. “The whole system will need some time to reset and release all the additional water.”

Multiple evacuation orders are in place across NSW, with a record-breaking flood warning being one of the gravest concerns for the Moree community.

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The record-breaking floods come on the back of record drought, heat and wildfires that hit eastern Australia in 2019 and 2020. This is in line with published in 2008 predicting that climate change would result in “longer dry spells broken by heavier rainfall events” in Australia.

“Climate change essentially means that extreme weather events are on steroids so they become more intense and frequent,” says Karoly.

The extremely wet conditions are in stark contrast to the hot, dry conditions across the US, Europe and China in recent months, which are also thought to be associated with climate change.