Christmas weather forecast: Festive season rain as Riverland prepares for highest water levels in 50 years

A soggy Christmas is on the cards for South Australia, with major weather events set to bring unseasonable conditions and high water levels to the state’s Riverland areas.

Emily Olle and Lauren Thomas-Nehmy

3 min read

October 20, 2022 - 11:28AM

Third La Nina season expected to arrive in Australia

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South Australia should brace for a wet and wild summer all the way through to the festive season, with the Riverland expected to be hit with the highest water levels in 50 years from early December.

Darren Ray, a former meteorologist at the Bureau of Meteorology and consulting climatologist, says South Australia can expect above-average rainfall and cooler temperatures through to the end of the year – with a soggy Christmas Day very likely.

Mr Ray studies cycles of tropical activity, which give an indication of potential rainfall and temperature months in advance.

WILD WEATHER

The Riverland is bracing for the highest water levels in 50 years, following heavy rain and flooding over the eastern border.

A team of engineers from the Environment Department along with SES volunteers will travel to Renmark to assess vulnerable areas including two levees of highest concern.

However, the effects of the wild weather aren’t expected to reach South Australia until early December – and even then, the Environment and Water Minister Susan Close believes the region should not expect a “major flooding event”.

The Department has predicted 120 GL of water will flow through the Riverland per day – the equivalent of 48,000 Olympic-sized pools.

Ms Close warned the forecast could be revised, but the state has time to prepare.

CHRISTMAS WEATHER IN ADELAIDE

Independent climatologist Mr Ray said rain was set to give way to finer, warmer days through the end of October, before the wet weather picked up again at the end of October to early November.

“We see these four to six week cycles where things are a bit suppressed and you get clearer skies and finer conditions, and then a week or so where you get bursts of increased tropical activity where you’re more likely to get rain events,” he said.

This pattern is set to follow through November and December, with cooler days at the end and start of each month giving way to sunshine through the middle.

So if your Christmas plans involve a poolside BBQ, it may be best to prep an indoor option now.

“There’s a chance we could have a wetter Christmas period, with a bit more of that stormy weather we’ve seen over the past few months,” Mr Ray said.

But beach-lovers shouldn’t despair too much, with things set to heat up during January – and the possibility of a “cracker heatwave” early 2023.

Adelaide’s wet weather will likely continue through to December. Picture: NCA NewsWire/Kelly Barnes

WHY SO MUCH RAIN?

Mr Ray said South Australia’s increased rainfall over the past few years was the product of two major weather events.

The first is La Nina, which increases winds across the equator, changing ocean currents and drawing cooler deep water from below – leading to above-average rainfall during the winter and spring months.

The Bureau of Meteorology announced last month that Australia was entering its third consecutive La Nina summer, which was expected to impact Australia through to December before easing in January.

While La Nina has a greater impact on northern and eastern states, increased rainfall can also be pushed down to South Australia.

The second factor is negative Indian Ocean Dipole (IOD). Similar to La Nina, IOD increases westerly winds across the equator, concentrating warmer than usual water in the east and cooler than usual water in the west.

These warmer waters increase available moisture, leading to increased rainfall across South Australia.

Mr Ray said the impact of both these events was heightened by climate change, with warmer ocean temperatures across the globe meaning more moisture was being evaporated for rainfall.

“In general, temperatures are over a degree warmer than they were 50 years ago which means the atmosphere can hold more moisture,” he said. “With warmer oceans, you also get more evaporation.”

“So when there is a La Nina around, climate change makes that much more intense.”