It’s nearly winter. So why are storms hitting Brisbane?

With winter just days away, it’s hardly storm season in Brisbane. Or is it?

Storms and heavy rain hit the city on Wednesday, alongside flash flooding further west, as a large, complex low-pressure system known as an “atmospheric river” made its presence felt.

Weatherzone meteorologist Ben Domensino said an upper-level, low-pressure system was passing – rather slowly – over south-east Queensland, destabilising the atmosphere.

“One reason this weather pattern is producing so much rain is because it is being fed by a steady feed of air from the tropics, which is also being boosted by additional moisture evaporating from the abnormally warm Tasman Sea,” he said.

“This setup is creating a conveyor belt of moisture, also known as an atmospheric river.”

The Bureau of Meteorology’s Daniel Hayes said a system moving east into south-east Queensland brought “decent thunderstorm activity” to the region on Wednesday afternoon, including heavy rain.

“The peak of the falls was at Dayboro, where we had 50 millimetres come down in about 30 minutes,” Hayes said.

Burpengary recorded about 30 millimetres over an hour, similar to the Redland Bay region, south of Brisbane.

Domensino said these weather systems were not uncommon in autumn and winter.

“But it’s unusual to see them stick around for so long,” he said. “This week’s system appears in no hurry to go anywhere fast.”

Bureau of Meteorology senior forecaster Christie Johnson said there was even a chance of hail on Thursday for parts of Brisbane.

“If we happen to get some of the biggest storms, we could also potentially see some large hail or damaging wind gusts. But heavy rainfall is probably the most likely severe hazard with storms,” she said.

Brisbane autumns typically hold the promise of crisp mornings followed by blue skies and relatively mild temperatures that require little more than a cardigan.

However, this May has been wet – really wet.

Last Monday, a massive cloudband stretched over much of the country and dumped more than a month’s worth of rain (about 60 millimetres) on Brisbane in 24 hours, flooding roads across the city and bringing trains to a halt on three major lines.

The Gold Coast broke a 20-year rain record for the month as nearly 200 millimetres fell over the region, prompting hundreds of calls for help to the State Emergency Service and leaving a group of students on a school camping trip stranded.

The average May rainfall for Brisbane is 69.2 millimetres. Brisbane is on track to record its wettest May since 2022, when 280 millimetres fell over the city.

“We’re already double the monthly average, and then we’re expecting more again,” Johnson said.

“We could end up with triple our monthly average.”

However, it will fall shy of the record set in 1996, when Brisbane copped 577 millimetres in the month.

The Gold Coast is experiencing its wettest May in 17 years. In May 2009, the Gold Coast recorded 339 millimetres of rain.

Already this month, the region has received 271 millimetres.

The unusual weather system was predicted to move offshore by Friday afternoon, making way for a sunny reprieve on Saturday morning that should last well into next week, giving residents a chance to dry out and finally hang some washing on the line.

“We’ll definitely get a chance to dry out over the weekend with lots of sunshine forecast,” Johnson said.

Sunshine is forecast for Saturday, Sunday, Monday and Tuesday, with temperatures maxing out at a pleasant 24 degrees.

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