During the period 17 – 18 August, a low pressure trough moved along the central and southern New South Wales coast, causing heavy rainfall. On 17 August between the hours 6 pm to 9 pm, a thunderstorm remained over the Wollongong area dumping heavy falls. Minor flooding had occurred on the days leading up to the storm, and on 17 August the flood peak occurred in most catchments between 7 pm and 8 pm. Due to the flash flooding, many areas were isolated until 9pm.
Major roads and train lines to Wollongong were disrupted and mudslides were reported on some roads, including Bulli Pass. A railway embankment failure at Coledale resulted in train delays for up to a week. Fifty homes were flooded in north Wollongong, and it was reported that homes along the coast were dislodged from their foundations. One person drowned while attempting to cross a flooded creek at Bellambi.
Damage recorded in Sydney suburbs included; erosion of beach side suburbs, 14 metropolitan roads blocked, power loss to thousands of homes and trees and power lines brought down by winds reported to have reached 92 km/h.
Due to the impact of the flood, the State Emergency Services (SES) obtained access to the Natural Disaster Relief Arrangements (NDRA) funding which assisted in the response efforts. During the cleanup operation up to 450 personnel assisted and 41 SES volunteer units sent teams into Wollongong.
Rainfall levels recorded for 24 hours to 09:00am on 18 August were:
Mt Ousley: 445mm
Bulli Pass: 410mm
The Insurance Council of Australia estimated the 1998 damage at $40 million, with the 2011 estimated normalised cost of $97 million.