New South Wales has included more local governments under the declared natural disaster areas, among which are Bourke and Tamworth in the state's north due to massive flooding.

Emergency Services Michael Gallacher told the media the declarations were made in consideration of the 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 extended declarations were announced as North Brewarrina residents were told to prepare to evacuate should the NSW State Emergency Service (SES) advices them to do so.

The SES said floodwaters from southern Queensland and northwestern NSW were entering the Barwon River system, bringing a threat of major flooding that could adversely affect North Brewarrina.