Sydney house fire blamed on lightning

A home in Sydney's northwest has been damaged by fire after being struck by lightning during thunderstorms that lashed the city overnight.

Firefighters spent an hour bringing the fire under control at the Epping home after it was reported by neighbours at around 6.30pm on Thursday.

A Fire & Rescue NSW spokesman told AAP the cause of the fire had yet to be confirmed but it was highly likely it was a lightning strike.

Emergency services had a busy night, with fire crews and SES volunteers responding to nearly 350 callouts across Sydney.

More storms are predicted to move across NSW on Friday afternoon.

The Bureau of Meteorology said Sydney would remain muggy for most of Friday with the temperature creeping into the 30s in city's west and a high chance of thunderstorms brewing in the late afternoon.