The NSW government has extended natural disaster declarations to Bourke and Tamworth in the state's north.
Emergency Services Michael Gallacher said the declarations followed widespread flooding which has damaged infrastructure, homes and businesses.
"These measures will help families, business owners and primary producers to restore any damage caused by the floods and ease some of the associated burden," Mr Gallacher said in a statement on Tuesday.
The local government areas of Walgett, Brewarrina, Liverpool Plains, Gloucester, Upper Hunter, Ballina, Gunnedah, Moree Shire, Greater Taree, Gwydir, Narrabri, Tenterfield, Bellingen, Byron, Lismore, Kyogle, Richmond Valley, Clarence Valley, Coffs Harbour, Inverell, Nambucca, Kempsey and Tweed Shire Council have already been declared natural disaster areas.
The new declarations came as residents of North Brewarrina were told to prepare to evacuate if told to do so by the NSW State Emergency Service (SES).
The SES said floodwaters from southern Queensland and northwestern NSW were entering the Barwon River system, bringing a threat of major flooding.
"As a result ... community members of North Brewarrina should prepare to evacuate if instructed to do so," the SES said in a statement.
"Community members should monitor the situation and be prepared to evacuate when instructed to do so.
"A Flood Evacuation Order will be issued ... if required."