The SES received 150 requests for help after storms hit parts of Sydney's west, with the weather bureau saying it's a typical summer scenario.
Lightning shows are set to continue across skies over NSW as an active system takes centre stage, causing damage in parts of Sydney, according to the weather bureau.
Weatherzone reported 4649 lightning strikes between 3am and 6am over Sydney on Tuesday.
The city's west and northwest were most affected by storm activity overnight, with the SES receiving 150 requests for help.
Strong winds caused roofs to come off and trees to fall, particularly in Blacktown, SES spokeswoman Sharon Fox said.
The weather bureau says lightning strikes will continue over the Sydney region and most parts of NSW on Tuesday.
Passengers can expect slight delays on domestic flights out of Sydney Airport, but international and domestic arrivals are on time, an airport spokesman said.
Meanwhile, rail commuters on Sydney's north shore T1 line can expect delays.
"It's quite an active lightning system over Sydney," BOM forecaster Jordan Notara told AAP.
He said the lightning will die down in the next couple of hours and build up again on Tuesday afternoon.
"It's a typical summer scenario," he said.
The SES has warned NSW residents to take precautions as the storm activity sticks around.
Residents are warned to secure outdoor furniture, tie down trampolines and stay inside and keep away from windows.