HEAVY rain, wild surf and gale force winds are expected to hit northern NSW this Australia Day long weekend.

The weather bureau says ex-tropical cyclone Oswald, which has already travelled 2000km south from Cape York, is tracking south and due to hit the state's north today.

The wild weather is expected to move south to the NSW Mid-North Coast tomorrow and Monday, with communities at risk including Ballina, Byron Bay, Grafton, Coffs Harbour and Port Macquarie.

The rainfall is expected to extend west of the Dividing Range, affecting Moree and Inverell, and south to eastern parts of the Hunter Valley, including Newcastle.

Gale force winds are likely to produce high seas and damaging surf conditions.