The search for a man missing in Lismore has been suspended due to flood water dangers, as a rain bomb continues to drench northern New South Wales.

NSW Police said on Sunday evening they will resume the search at first light on Monday.

They say officers from Richmond Police District were near Brewster Street and Uralba Street in Lismore about 4pm when they saw and heard a man calling for assistance from nearby floodwater.

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However, police lost sight of the man a short time later.

The man was last seen in Lismore and police believe he may have gone down a drain.

NSW SES Chief Superintendent Steve Patterson said the weather system was inundating the northern rivers and mid-north coast, and rain was forecast to keep coming.

"The predictions are that we will see about 150-250mm of rain within 24 hours across that widespread area," he said.

Mr Patterson added that in some isolated areas there may be as much as 500mm.

There is an evacuation warning in place for large parts of Lismore as the Wilsons River continues to rise.

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Further evacuations had been ordered for Tumbulgum and surrounding areas, and multiple evacuation warnings issued by the NSW SES on Sunday night.

The NSW SES said the river levels are likely to exceed the moderate flood level of 7.2 metres on Sunday night.

The river level may reach the major flood level of 9.7 metres early Monday, with rises to 10.6 metres possible during Monday, the SES warned.

The evacuation warning is in place for low lying areas of North Lismore, South Lismore, Lismore CBD, East Lismore, and Girards Hill.

"Low lying properties may experience impacts due to flash flooding and or riverine flooding," the warning from the SES says.

"Storm and flood impacts may interrupt essential services such as electricity, phones, internet, water and sewerage.

"People in these areas need to closely monitor weather and road closures and make informed decisions early based on individual circumstances.

"Residents should monitor the situation and be prepared to evacuate when instructed to do so.

"A Flood Evacuation Order will be issued by the NSW SES if and when evacuations are required."

An evacuation warning has also been issued for Mullumbimby, areas near Maclean on the Clarence River, as well as Chinderah and Fingal Head near the Tweed River.

In the Tumbulgum region, an evacuation order is in place.

Across the border in south-east Queensland conditions are worsening with Premier Annnastacia Palaszczuk describing the storm as "like an unpredictable cyclone".