The heavy storm that hit Kiama at about 3am on Sunday brought with it 90km/h winds and massive amounts of rain.
Julie Evans from the Bureau of Meteorology said the average wind speed at Kiama when the storm hit at 3am was 60km/h gusting up to 80 or 90km/h. Also about 70ml of rain fell between 3am and 4am.
The storm was part of the same system that has caused flooding in the north of NSW.
Towns in northern NSW like Kempsey, Grafton and Port Macquarie are experiencing significant flooding, affecting 20,000 residents after the storm passed through earlier this weekend.
"We had a low pressure system that started off the coast of Queensland," said Julie Evans from the Bureau of Meteorology.
"It tracked south and crossed the NSW coast around Coffs Harbour on Friday afternoon.
"The low's actually moved inland but the belt of strong winds and rain associated with it has very much focused on the coast.
"That has moved steadily southwards as the weekend has progressed, so the heaviest rain in the last 24 hours has been in the Illawarra and the Central Tablelands."
The band of heavy rain and winds that tracked down the coast linked up with a thunderstorm that brought its own winds with it.
"Usually thunderstorms only affect a small area of about 10 kilometres and only last for a few minutes but what we saw was a broad-scale enhancement of the winds as they moved down the coast," Ms Evans said.
"It's a broader-scaled system but within that there are localised areas that have an even worse experience because there are thunderstorms associated with them."
Ms Evans said, in weather conditions like this, it is the more exposed areas that can be hit the hardest.
"Kiama is quite an exposed area, really," she said.
"It's got all that high ground. The places that are a bit more exposed are often the places that get more damaged in situations like this."
The Bureau of Meteorology has cancelled the severe weather warning for the region but Ms Evans said there was still a strong likelihood of thunderstorm activity this afternoon.
"If any of those thunderstorms look like becoming severe we will be issuing severe weather warnings this afternoon," she said.
"By severe, they're thunderstorms than can bring strong wind gusts but also can bring very heavy rainfall. If you get a series of storms moving over the one area that can bring prolonged heavy rainfall.
"If that looks like happening we will issue further warnings this afternoon."