NSW has sloshed through its equal wettest week since records began after an ''extraordinary'' weather event dumped unprecedented rain across the state and forced thousands to flee their homes.
New data from the Bureau of Meteorology released yesterday showed an average 123.9 millimetres of rain fell across the state last week - a record deluge not seen since January 1974.
It was triggered by a slow-moving rain band and low pressure trough which brought tropical moisture from the north-west and north-east, toppling records at numerous rainfall stations and catchments.
At Charlotte Pass, 186.5 millimetres fell in one day. Record weekly rain fell at stations with century-long data collection, such as Ivanhoe Post Office (294 millimetres), Wilcannia (239.8 millimetres) and Hay (189 millimetres). The bureau described the record-breaking rain as ''extraordinary''.
''It is very rare to have such persistent, record-breaking rainfall over such large areas of NSW and Victoria,'' NSW climate manager Aaron Coutts-Smith said.
Residents in Sydney, the Illawarra, the Hunter and South Coast were last night on high alert amid predictions of more heavy rain, thunderstorms and flash flooding.
Damaging waves are expected to pound the coast this morning, causing coastal erosion and dangerous beach conditions. Conditions are expected to ease in the afternoon.
Elsewhere across the state, the flood threat in Wagga Wagga eased yesterday.
However, water levels remained high in the northern part of the city, preventing residents from returning to their homes.
Prime Minister Julia Gillard promised Wagga Wagga residents they would get all the assistance they needed to rebuild their community once the full extent of damage is known.
Ms Gillard arrived in the Riverina city yesterday, after floodwaters peaked at 10.56 metres and began to ease through the morning.
She met SES workers to thank them for helping prepare locals for the worst, which was narrowly averted after the city's levees held fast against the raging and swollen Murrumbidgee River.
''In Australia we know we face these kinds of disasters only too often for a nation that over the last two years has seen so much hardship caused by floodwaters,'' she said.
''Now we're seeing that hardship here.
''But whenever we see that hardship we see some great Australian spirit, and I've seen that in spades today.''
Ms Gillard boarded a helicopter to view damage to properties from the air.
''When the flood water subsides, then we will be able to count the cost to infrastructure, and we will be working with the state government and with local governments to assist with getting infrastructure back in order,'' she said later.
Meanwhile, the Lachlan River at Forbes is expected to peak tomorrow at 10.65 metres. Rising flood waters split the town into three yesterday, cutting off main roads and inundating the CBD with water.
Matthew Duff, a Forbes wheat farmer, said he wouldn't be able to sow a crop this year as the ground would remain too wet.
''We're copping it pretty badly at the moment,'' he said.
''The one good thing is that we haven't put the winter crops into the ground yet. If the water came up in a couple of months time we'd have wasted a lot of money on seed and fertiliser.''