Bureau of Meteorology spokeswoman Morgan Pumpa said the volatile weather system that was over the north east of NSW moved off-shore and intensified before moving its way back to land. However, she said the coast was copping a lot a rain associated with the front on Wednesday.

Ms Pumpa said the Bureau had updated their flood alerts around 11am, as their modelling showed it was predicted to impact land further north than first thought.

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She said the Illawarra was still expecting more "heavy to intense rainfall due to low pressure system" on Wednesday and into Thursday, with Macquarie Pass already recording 58mm of rain between 9-11am.

"At any point it could speed up or slow down due to the atmosphere and what's happening within it," she said.

"The intensity could change ... this system it is drawing from the warm sea surface temperatures .. that can change how intense it is, and how quickly it's getting moved by a high pressure system sitting below NZ and other factors that are out of our control."

It's still expected parts of the Illawarra and South Coast could be inundated with more than 200mm of rain in the next 48 hours, with rain expected to ease slightly on Friday and Saturday before ramping up again.

"Even into the weekend as we expect to see this low pressure system weaken, there's still the chance of rain on Sunday in the Wollongong area of 20-40mm predicted," Ms Pumpa said.

She said rising rivers were also posing a concern with the continued heavy rain.

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