A low pressure system from the south-west brought lightning to the Illawara on Sunday afternoon, and Weatherzone's Graeme Brittain said there were thunderstorms over Sydney's north shore and Mascot.

Mr Brittain said there was the chance of another storm on Sunday night but he thought it unlikely. He said rains would ease off into the sea, leaving a mostly dry night.

But wetter weather is on the way, with a low pressure system affecting south-east Australia set to arrive on Thursday.

"Models are indicating quite a deep area of low pressure in south-eastern Australia, affecting Adelaide, Melbourne and Sydney, bringing strong winds and heavy rainfall in some places," Mr Brittain said.

"It will arrive in Sydney on Thursday and then linger through until the early hours of Saturday."

Melbourne and Adelaide will receive the brunt of the system's rainfall while Sydney will contend with strong winds.

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