Thunderstorms rolled through the Illawarra overnight with more than 4600 lightning strikes recorded in the greater Sydney area between 3am and 6am.
Weatherzone Senior Meteorologist Jacobus Cronje said the Tuesday morning thunderstorms were more severe than Monday evening's.
"It is way more [lightning strikes] than we had yesterday, it's a similar set-up but just more intense, more moisture," he said.
More rain and gusty winds are forecast across the Illawarra on Tuesday with the chance of another thunderstorm likely, according to the Bureau of Meteorology.
In Sydney, lightning damaged signal equipment at Gordon, disrupting services between Gordon and Chatswood on the T1 North Shore Line.
Trains were briefly halted, and while the service has resumed Transport NSW said passengers should still allow extra travel time.
Thunderstorms will likely flare up again in the afternoon, and while the Senior Meteorologist said there were no severe thunderstorm warnings yet forecasters were expecting some serious storm activity across the coast in the afternoon and early evening.
And while there will be no relief from a sea breeze, temperatures are set to drop later on Tuesday.
"We're actually expecting a cool change in any case later this evening,"Mr Cronje said, adding daytime temperatures are expected to drop between six and eight degrees.