The Bureau of Meteorology has issued a severe weather and hazardous surf warnings for the Illawarra, South Coast, Sydney and up to Gosford.

Damaging winds averaging 60 to 70 km/h with peak gusts in excess of 90 km/h are possible along the coastal fringe of Illawarra, northern parts of the South Coast districts and metropolitan Sydney from late today onwards.

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Temperatures have plummeted with a top of 15 degrees expected.

A transient low pressure system will then form within the front, deepening off central coastal waters late today and generating vigorous winds and sea over central and southern waters.

This low is expected to move slowly east during the mid week, with conditions easing as it tracks into the Tasman Sea.

Winds are expected to gradually ease below gale or damaging wind thresholds during Wednesday morning.

The low pressure system is expected to deepen through Tuesday and into Wednesday, bringing rising swell through Tuesday, peaking on Wednesday morning.

Forecast swell conditions could reach six metres offshore on the central and southern coastline.

It is anticipated this will impact the Far South Coast to the Mid North Coast.

Conditions will be hazardous for coastal activities such as rock fishing, boating, surfing and swimming.

People should consider staying out of the water and rock fishers should avoid coastal rock platforms exposed to the ocean.

Kiama Council has closed its rock pools and beaches due to the risk of pollution from heavy rain and stormwater runoff, as well as the forecast for rough surf conditions.

SLSNSW Director of Lifesaving Joel Wiseman has urged the public to exercise caution if they are visiting the coast.

"These conditions have the potential to cause high winds which can be dangerous for rock fishing, boating, surfing and swimming," he said.

"With the current COVID environment our resources aren't committed to actively patrolling until mid-September, so if you take a risk and find yourself in trouble there could be a delay in response in getting emergency services to the scene.

"People are strongly urged to check BeachSafe and understand your limitations if you do decide to take a risk."

Surf Life Saving NSW club call-out teams, duty officers and surf rescue assets are on standby to respond to critical coastal incidents, despite it being off-season.

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