Water continued to surge into the Killick Creek beach outlet overnight, after spilling into to the reserve at the holiday park at Crescent Head yesterday at high tide.

People are urged not to enter the water today with many beaches closed from as far south to Forster and north to Nambucca Heads.

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

Weather warnings remain in place.

"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 north of Seal Rocks.

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 for the Mid North Coast.

NSW Police Force, Marine Area Command advise that:

NSW SES superintendent Mark Elm said that volunteers from across the northern coastal areas are keeping a close eye on the situation and have put their hand up to be ready in case local communities feeling the impact of the predicted weather need their support.

"The NSW SES volunteers are checking equipment and readying teams for support if needed," superintendent Elm said.

"Volunteers have been working over Christmas and New Year and are again demonstrating their incredible commitment to serving their local communities this week if needed.

"Although our volunteers are ready to help if necessary, we are asking that people do some simple things so that your property can be as safe as possible," superintendent Elm said.

"Be sure that you keep your house free from overhanging branches that can come down in high winds and damage your roof. Put away furniture and play equipment that can be picked up by winds and blown into houses and overhead powerlines. Make sure that you have a battery powered radio on hand so that if you lose power you can stay up to date with the situation by listening to your emergency broadcaster."

"These small things might mean the difference between your home being safe and undamaged or unnecessarily affected by the impact of severe weather."

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