Monday is tipped to be the wettest day of the week with between 20 and 40mm of rain predicted, according to Weatherzone.

It's all due to an East Coast low expected to form off the NSW coast on Monday, bringing heavy showers, strong winds and dangerous surf to much of the coast.

Showery conditions look to persist to Wednesday with Wollongong picking up more than 30mm.

Weatherzone reports say the Illawarra could exceed its monthly average of rainfall.

Conditions are looking to ease slightly on Thursday.