A wild storm wreaked havoc in the Illawarra, the Southern Highlands and Bargo on Thursday night.
The SES were called out to 20 jobs across the region, including a flood rescue in Wollongong.
Emergency crews also removed several cars trapped on Springhill Road.
As many as 150 cars were reportedly banked up to the west and east of the Cringila Road turn-off
The road was cut off by flash flooding, forcing crews to remove the cars at risk of being washed away.
SES volunteers were also at Bargo assisting with the clean up.
Residents said lightning had been striking from all directions.
"We've been here 11 years and I don't think I've seen anything like it," Bargo Motor Inn owner Jeanette Briggs said.
She said a friend had been dining at the Bargo pub when an awning, about 30 metres long, blew off the roof and onto the nearby railway line.
"Lucky nobody was killed," she said..
A small gas main was also damaged when a large tree was struck by lightning, a spokesman for the Jemena gas company said.
Local firefighters switched off the gas and supply was not affected.
The Southern Highlands rail line between Picton and Moss Vale was partially closed for several hours, due to a fallen power pole and debris on the tracks.
It re-opened on Friday morning.
Meantime, the flooding also partially stopped trains on the South Coast line on Friday morning.
Buses continue to replace trains between Wollongong and Port Kembla.
The Bureau of Meteorology said the storms were part of a southerly change coming through the region and moving to the north-east.
"The line of storms extends all the way back into the hills in the back of Sydney," senior forecaster Jane Golding said.
"[There is] a lot of lightning and some very heavy rainfall," she said.
Ms Golding said the area just west of Wollongong received 100 millimetres of rain over just one hour.
-AAP & smh.com.au