Shortly before noon on Friday, the Bureau of Meteorology (BOM) issued a flood watch warning for the region.

It said the Newcastle catchment is likely to be affected by a potential East Coast Low, with a minor flood alert for Wollombi Brook and Lower Hunter River, Lake Macquarie and the Central Coast along with the Paterson and Williams rivers.

MINOR FLOOD WARNING

"Heavy rainfall associated with a potential East Coast Low is forecast to develop through central parts of the NSW coast from the Hunter to the South Coast during the weekend and into early next week," the BOM warning said.

"This heavy rain may cause minor to moderate flooding along parts of the Hunter, Central Coast, Greater Sydney and South Coast. Major flooding is possible in the Hawkesbury Nepean Valley over the weekend."

At around 1.30pm on Friday the BOM issued a hazardous surf warning for the Hunter Coast on Friday and Saturday.

Flooding is no longer expected in the Manning and Gloucester Rivers, Wallis Lake, Myall River and Karuah River.

The BOM has predicted 10 to 15mm of rain for Newcastle on Saturday and up to 50mm an 80mm for Sunday and Monday respectively. There is an at least 95 per cent chance of rain from Saturday through to Wednesday, July 6.

Rain is anticipated to be heavier south of Newcastle, with the BOM predicting up to 120mm for Gosford on Sunday and 100mm Monday.

On Friday the BOM also issued a severe weather warning for Sydney and the Central Tablelands, with six-hourly rainfall totals between 80 to 150mm are possible.

"If an East Coast Low does form, damaging wind gusts will become a risk late on Sunday and into next week, depending on the strength and location of the low," the warning said.

Senior BOM meteorologist Jordan Notara said on Wednesday the Hunter can expect higher than average rainfall for the remainder of July, with the BOM website showing an 80 per cent chance of above average rainfall for the entire region between July 2 and July 15.

"Suggestively it looks to be a mixed bag for the rest of July," Mr Notara said.

"The higher than average rainfall may come from single weather events like the coming week rather than persistent rain for the month."

The State Emergency Service (SES) has advised people not to drive, ride or walk through flood water and to keep clear of creeks and storm drains.

"If you are trapped by flash flooding, seek refuge in the highest available place and ring 000 if you need rescue," the SES said.

The SES also warned people to be aware that run-off from rainfall in fire affected areas may behave differently, be more rapid and contain debris such as ash, soil, trees and rocks.

"After bushfires, heavy rain and the loss of foliage can make the ground soft and heavy, leading to a greater chance of landslides."

Commissioner Carlene York has advised people who were not affected by the last flood not to assume that they won't be this time.

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