There was flooding reported in Cardiff, Mayfield, Wallsend and low-lying parts of King Street in Newcastle city centre. Further afield, torrential rain in Dungog saw the State Emergency Service on high alert and the community on flood watch.

Local school students were sent home early in Dungog to avoid road closures, while Plattsburg Public School at Wallsend was forced to evacuate students and staff after the nearby stormwater drain in Federal Park burst its banks.

AS IT HAPPENED: FOLLOW THE WEATHER EVENT HERE

A FORECAST dumping of a month's worth of rain in a single day has put emergency service workers on notice amid fears parts of the Hunter could experience flash flooding.

State Emergency Service volunteers were on Tuesday afternoon handing out sandbags after the Bureau of Meteorology issued a severe weather warning for large parts of the Hunter, including Newcastle, Lake Macquarie and Maitland, with a forecast 200mm to fall in some places on Wednesday.

The bureau predicted the rain would start to fall late on Tuesday night and persist throughout the week.

“But we will see most of it within one day ... it will be intense,” meteorologist Jordan Notara said.

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The bureau's official March rainfall record for the Nobbys weather station is 283.7mm. The weather event, caused by a coastal trough cradled between two strong high pressure systems, is still expected to nearly double the March rainfall average of 119.8mm (Williamtown), even if the deluge is unlikely to be record-breaking.

There was a flood warning in place for the following locations: Newcastle, including Wallsend and Hexham, Lake Macquarie, Central Coast, Wollombi, and areas near Wallis Lake and the Manning, Myall, Karuah, Paterson and Williams rivers.

Hunter Region SES spokeswoman Raechel Squires said there was a broad warning in place because the weather pattern was “unpredictable” and “uncertain”. 

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“You simply do not know where that rain will fall until it does,” she said. “Do not wait until it is too late. Now is the time to be prepared.”

Stockton, which suffered badly with erosion after huge swells in January, is also likely to take a battering on Wednesday thanks to a 2.5-metre swell predicted for the Hunter coast.

A separate warning was in place for hazardous surf conditions, including strong winds. The winds and storms could extend well into the Hunter.

“It will exacerbate the problem,” said Stockton Residents Action Group spokesman Keith Craig on the potential for further erosion in the seaside suburb.

“If it’s a southerly swell, it will affect the childcare centre. If it’s an easterly, it will hit the surf club.”

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Newcastle City police Inspector Shane Buggy said dangerous driving conditions were likely.

Residents were warned not to enter floodwaters, with problem spots for water over the road including Newcastle Road and Industrial Drive.

“We are urging motorists to obey police directions and show patience,” he said.

The Upper Hunter, including Scone, which has been very dry, is forecast to receive smaller amounts of rain than the coast.