Wild weather has swept across eastern Australia, with the NSW State Emergency Service reporting flash flooding, persistent heavy rain continuing in parts of the ACT, Victoria and Queensland and severe thunderstorm warnings issued.

The Bureau of Meteorology says the heaviest rainfall totals overnight were across the NSW Illawarra and South Coast districts, mainly between Nowra and Bega, with Jervis Bay Airfield receiving 225mm, and falls of 100-200mm widespread.

Senior Meteorologist Angus Hines says two-day totals in the region could exceed 300mm in some areas.

The SES conducted two rescues at South Nowra and St Georges Basin, near Jervis Bay this morning, while floods inundated low-lying areas of Lake Conjola. A large number of calls for assistance were received in the Deniliquin region.

“Rain is being driven onshore by a deep low-pressure system over central NSW steering in a persistent feed of moisture from the northeast,” Mr Hines told a media conference. “It is not really until the end of the week and into the weekend that we expect the rainfall and the flooding risk to start to subside more significantly.”

Warnings for damaging winds, large hailstones and heavy rainfall were issued for regions including the Sydney area and Greater Wollongong this afternoon.

In Victoria, Swan Hill received 85mm of rain by 9am, with much of that falling after 1am. Some northern areas are likely to receive more than a month’s rainfall in a few days in conditions “reasonably unusual” for this time of year.

“We are expecting a lot more rainfall to fall over parts of Victoria in the coming couple of days, particularly the far east,” Mr Hines said.

“It is the Gippsland area which becomes the focus of the heaviest rainfall for tomorrow and towards the end of the week, where we expect over 100mm of rain to fall particularly east of Bairnsdale.”

Heavy rainfall and storms have also hit SA this week, with flash flooding reported and thousands of homes affected by power outages.

The rain has fallen amid expectations that Australia could be in for a drier summer compared to recent years due to the swing this year to an El Nino event.

Mr Hines says the bureau is anticipating quite a warm summer, but the correlation between El Ninos and dry weather tends to stand out more strongly in winter and spring, and large parts of Australia are expected to receive around average rainfall over the next few months.

Aon Senior Catastrophe Research Analyst Thomas Mortlock says this week’s weather is a reminder that such troughs can still form under El Nino conditions, and it will be necessary to wait until well into the autumn before the impact of the event can be properly assessed.

“They say no two El Ninos are alike, but this one is doing a pretty good La Nina impression at the moment,” he says on LinkedIn.

“Something that is often overlooked - perhaps because it occupies the ‘twilight zone’ between weather and climate modelling - is that the multi-decadal state of the Pacific Ocean is still La Nina-like and has been for the past ~25 years.”

A shift in the background state is overdue, but until that occurs “we’ll continue to have El Ninos and La Ninas over background La Nina”, he says.