The south-east region of New South Wales could receive up to 200mm of rain before the end of the week, adding to already soaked catchments and high rivers that have flooded across the state.
The heavy falls could deliver some areas their total monthly average. A broader trend will see rain across all of eastern NSW for the rest of this week.
It is due to a low pressure trough moving east, meeting with a band of humid air.
The Bureau of Meteorology issued a severe weather warning on Wednesday afternoon.
Heavy rain and strong wind would “set the scene for further flooding and community impacts”, particularly on the south coast, the BoM meteorologist Jonathan How said.
Flood warnings were active around NSW and How warned “rivers will respond quickly”.
Severe storms expected in the central-east and north-east of NSW “may impact already saturated catchments such as the Namoi, Gwydir, Macintyre and Macquarie, which were recently affected by moderate to major flooding”, the bureau said.
There was also a chance of storms continuing throughout the week.
The NSW State Emergency Service responded to about 200 calls for help during and after storms and some hail pelted Sydney, the Blue Mountains and the Central Coast on Tuesday night.
Most of the calls were for storm damage on the Central Coast and in Sydney’s western suburbs. Authorities were watching the heavy rain forecast for the rest of the week.
“Probably the area of concern is really around the flash-flooding risk, people driving through flood waters or being caught in flood waters,” the SES assistant commissioner, Nicole Hogan, told the Nine Network on Wednesday.
“If you come across flood waters, please take an alternative route. Our volunteers have been working tirelessly since November 10 with the flooding in the west of the state.”
The Bureau of Meteorology also issued a strong wind warning for the Sydney coast and Illawarra coast on Wednesday.
The SES was also called to three rescues overnight in flood-affected areas. One woman was rescued when a flash flood went through a campsite at Casino in the northern rivers area, and another person from a car at Rocky Creek near Narrabri.
An SES spokesperson said there were about 300 volunteers helping in flood-affected communities and planning was under way to maintain a presence in western NSW until February.
Floods were expected to continue for a couple of months in western NSW with slow-moving flood waters coming down from Queensland and continual rainfall predicted across some of those areas.
Numerous homesteads were in for a soggy Christmas in western NSW and towns including Mungindi, which straddles the Barwon River on the Queensland border, the spokesperson said.
“We are expecting … as that flood water moves downstream there will be communities, townships and rural properties that will be isolated moving into Christmas.”
Multiple rivers across the state were still flooding, with waters expected to remain high for weeks.
Renewed river level rises and flooding were possible across the Upper Macintyre, Gwydir, Castlereagh, Peel, Macquarie and Belubula rivers on Wednesday afternoon.
Heavy rain on Thursday could cause flooding along the Snowy, Upper Murray and Mitta Mitta rivers.
Rivers that were currently flooding could rise as well including the Lachlan, Namoi, Macquarie and Bogan rivers.
Flood warnings were in place for much of the state’s inland river system including the Kingdon Ponds, Namoi, Macquarie, Bogan, Lachlan, Murrumbidgee, Warrego, Paroo, Barwon, Macintyre and Weir rivers.
On the south coast, the Moruya, Deua, Tuross, Bega, and Towamba rivers could also be affected in the coming days.