Further heavy rain is expected today and the State Emergency Service (SES) has advised residents to prepare for potential flash flooding further south on the coast.

A spokeswoman for the Bureau of Meteorology said the rain was isolated, with 99mm falling at Balgownie but only 34mm at Bellambi.

SES Illawarra region controller Greg Murphy said his crews received 60 calls between 10.30pm and midnight.

‘‘A number of those calls were to assist people who had water going through their house or were trapped in their vehicles,’’ he said.

‘‘Luckily the water dissipated almost as fast as it came up.’’

At North Wollongong, drivers had to be rescued from their cars which were inundated with water.

The North Wollongong PCYC suffered extensive damage, with club manager Michael Jones describing the situation as a ''huge blow''.

It remained uncertain whether insurance would cover a repair bill that could run into the tens of thousands, he said.

GALLERY: The aftermath of the Illawarra's flash floods

The debris discovered this morning illustrated the power of the flood waters; a shipping container on a building site in Virginia St, North Wollongong was swept along in the flood water and almost washed into Fairy Creek.

Fire and Rescue NSW and Wollongong police were called to assist the SES.

Acting Sergeant Paul Fitzpatrick said police attended 42 jobs .

‘‘We had a lot of cars floating down Stewart St. They were floating from one roundabout to the next,’’ he said.

Heavy rain also fell overnight at Foxground, which recorded 92mm of rain.

A severe thunderstorm warning which included a western part of the Illawarra has been cancelled.

The SES has prepared for potential flash flooding in the Bega and Moruya areas later today.