The Bureau of Meteorology said ex-tropical cyclone Seth is currently located over the southern Coral Sea.

"This system is forecast to adopt a west to northwesterly track, approaching the Queensland coast during the first half of the week. This system is generating increasing seas and swell, which will coincide with an astronomical peak in high tides over the coming days," a spokesperson said.

Abnormally high tides, which may cause sea water flooding of low lying areas, are possible for coastal areas.

Water levels could reach or exceed the highest tide of the year by at least 0.1 metres during the morning's high tide on Monday, Tuesday and possibly Wednesday mornings.

The Bureau said an increasing easterly swell is combining with strong to gale force winds to generate deep water wave heights at or above five metres in northern waters.

"This is likely to continue generating damaging surf conditions along the exposed southeast coast until Tuesday, and in conjunction with abnormally high tides could lead to coastal erosion, particularly for east facing zones," the BoM said.

A hazardous surf warning is current.

NSW Police Force, Marine Area Command advise that:

The south coast has experienced a run of hot, dry conditions due to a low intensity heatwave.

Surf Life Saving NSW Director of Lifesaving, Joel Wiseman said there was a pent up desire to get out and enjoy the outdoors after a year of lockdowns.

"Many people are moving around the state and visiting coastal holiday spots that they may not be familiar with. It's a high risk time and we implore everyone to heed surf safety advice and amend their activities to suit the conditions."