Thunderstorms have rumbled across Sydney for the ninth consecutive day, with more thunder and lightning on the horizon throughout Monday.

Sydney experienced a total of just two stormy days last summer, according to Weatherzone meteorologist Brett Dutschke.

But eight days into this summer, and that figure has already been well and truly eclipsed.

Leftover from storms in Sydney's north-west brought more rain and thunder, and a dawn rainbow. Photo: Nick Moir

At dawn on Monday, two main thunderstorms swept across Sydney. One came in off the Blue Mountains and moved swiftly through Penrith and towards Campbelltown, Mr Dutschke said.

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Another storm over the Hawkesbury moved through the Hills District and towards Sydney's northern beaches just after 6am.

"These are fairly fast moving, only lasting 10 to 15 minutes all up," Mr Dutschke said.

A full rainbow encircled the city, as seen from Potts Point. Photo: Cedric Tourasse

"There's a chance of another storm this morning, because the activity is still fairly significant on the Blue Mountains. We could see another storm or two during the morning but it looks like we will have a dry break between the early storms and the ones to develop later in the morning."

Mr Dutschke said there was a risk of severe storms again on Monday afternoon as the temperature heated up. A maximum of 30 degrees is forecast in the city and 35 degrees in the west on Monday.

On Sunday evening, a nasty thunderstorm lashed the city, forcing the temporary closure of the Tropfest site in Centennial Park. It was the latest storm to deliver damaging hailstones, raging winds and flooding from torrential rain.

Those gazing skyward over the past nine days have been treated to some spectacular sights, including dramatic storm clouds descending across Sydney.

Monday was no different, with a brilliant yellow sunrise and a full rainbow across the city.

"The storm cloud started to shift offshore, so once the cloud is out to the east of us it makes the sunrise all the more impressive," Mr Dutschke said.

He said storms were much less likely on Tuesday, but could re-develop on Wednesday.

A cooler change coming through on Thursday was likely to bring an end to the run of stormy days, Mr Dutschke said.

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