The Bureau of Meteorology warns that very dangerous thunderstorms heading towards Brisbane were detected on the weather radar.
Sydney is set to get a soaking as severe thunderstorms continue to drench much of NSW.
Tuesday's storms may lead to flash flooding for areas in the state's northwest and central areas, the Hunter, Central Coast and Sydney metropolitan, including the Blue Mountains, according to the Bureau of Meteorology.
Areas around Moree, Gunnedah, Narrabri, Nyngan, Newcastle, Gosford, Penrith and Springwood are in for heavy rainfall and damaging winds, according to BoM's latest severe thunderstorm warning as storm cells move through the state.
Up to 45mm of rain is expected to fall in Sydney's CBD on Tuesday with Penrith in the city's west set to receive up to 70mm.
Hailstones the size of golf balls may also continue to pummel the storm-affected northern and central NSW towns.
Easterly and northeasterly winds ranging from 15 to 40km/h will whip up the state across the day.
SES crews responded to about 230 jobs across "a large stretch" of NSW since the rain began on Monday, particularly around Dubbo where more than 69mm fell.
The call-outs were fairly minor including leaking roofs in the Blue Mountains and western parts of Sydney, SES spokeswoman Becky Gollings said.
"An aged care facility down at Albion Park was struck by lightning, although we didn't have any evacuations or injuries."
SES crews will keep an eye on roads in Sydney and the Illawarra that are prone to flooding.
Residents have been advised to prepare by clearing drain pipes and gutters, keeping at least eight metres away from fallen power lines, unplugging computers and appliances during the storm and staying indoors.
By Tuesday morning, NSW public transport system had already taken a hit from the wild weather.
Buses have replaced trains between Mount Victoria and Lithgow on the Blue Mountains Line due to damaged equipment from lightning strikes, according to the Transport Management Centre.
The South Coast Line is also expected to be affected during the afternoon peak due to the partial derailment of an empty train.
Passengers are advised to allow extra travel time and listen for announcements.
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