EMERGENCY services are preparing for flash flooding in the Northern Rivers, northern parts of Mid-North Coast and in eastern parts of the Northern Tablelands.
The Bureau of Meteorology has issued a dangerous thunderstorm warning for areas including Lismore, Grafton, Coffs Harbour, Port Macquarie, Sawtell and Dorrigo, and the storms are expected to hit in the next few hours.
BoM is predicting rainfall in excess of 100 mm in the north east over the next 24 hours. In the past three hours alone, Goonengerry in the Northern Rivers, to the southwest of Mullumbimby, has been drenched with 156 mm of rain.
Five river systems in northern NSW are on flood watch while soaking rain in Sydney is set to continue.
In Sydney, Blacktown, Erskine Park and Prospect have become Sydney's wettest suburbs, with all three recording over 60mm of rainfall in the past 24 hours.
75 mm has been recorded in the last hour at Gooengerry (SW of Mullumbimby).
The thunderstorms and heavy downpours have kept the NSW State Emergency Service busy, responding to 40 jobs since yesterday morning and undertaking four rescues.
Two drivers had to be rescued in Erskine Park after attempting to drive their vehicles through flood waters and a third was rescued in Toongabbie.
Yesterday afternoon, a throng of toddlers and pre-schoolers found themselves in the middle of a real life adventure, when the overflowing South Creek in Orchard Hills just south of Penrith cut the Old MacDonald's Child Care centre off from parents arriving to collect their children.
About 90 youngsters were loaded into an SES truck and NSW Rural Fire Service tanker and ferried into the arms of anxious parents.
SES Western Sydney evacuated 90 children from a child care centre in Orchard Hills, south of Penrith. Picture: Facebook
An SES spokeswoman said many drivers were still not heeding the warnings on the dangers of attempting to drive through flood waters.
"We're trying to get that message through and there's concern the storms are going to keep moving up to the north east of state," she said.
"There's still a flood warning for the northern rivers, so we're urging people planning to head that way to go to Live Traffic, check conditions, and don't drive through flood water. Too many people think their car is more invincible than it is."
The SES said the number of people having to be rescued from cars in flood water has risen correspondingly to the number of 4WD vehicles on NSW roads over the past 20 to 30 years.
Last year engineers at the University of NSW's Water Research Laboratory proved just how easily cars could be washed away, even in low water depths and slow flow speeds.
Using a specially configured test tank, the engineers found that a small car such as a Toyota Yaris, weighing 1.05 tonnes, could completely float away in 60 cm of water.
Even a 2.5 tonne Nissan Patrol 4WD could become water buoyant in just 95cm of water.
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