The combination of a high pressure system over the southern Tasman Sea and a trough over Queensland directed moist east to north-easterly winds across New South Wales. This generated patchy rain areas and isolated thunderstorms and heavy rain over the north of the state.

Minor to major flood warnings were issued for communities on the Mid North, Coffs Harbour and North Coast of New South Wales. There were reports of 300 mm falling in the space of three days in areas of the Bellinger River Valley and the Orara River catchment.

More than 2000 people were isolated by the rising floodwaters, with a number of road closures such as at the Pacific Highway and a caravan park in a low lying area evacuated.

From the 24 - 25 January New South Wales received almost 340 mm of rain. Overnight on the 24 January, the Tweed Valley saw heavy falls with 86 mm of rain at Couchy Creek, 100 mm at Numinbah and 100 mm at Bald Mountain.

Residents were isolated in the towns of Darkwood, near Coffs Harbour, the Thora and Kalang Valleys, and in Bellingen, on the Mid North Coast, where the flooded Bellinger River cut the town in two. More than a dozen homes and businesses in Bellingen were inundated. The Bellinger River at the Bellingen Bridge peaked at around 7 m, short of the 8.2 m that constitutes major flooding.

A landslide and waterfalls blocked the Waterfall Way between Dorrigo and Bellingen. Bellingen received 180 mm of rain in the 24 hours to 9 am on 27 January.

During this time the State Emergency Services received more than 1000 calls for assistance and over 50 flood rescues occurred.

By the beginning of February more than 16,500 people across the state were isolated, with the worst areas being Gunnedah and Wee Waa. Twenty-seven aircraft worked to supply those areas isolated.

On 5 February the Namoi River peaked at over 8 m in Gunnedah and the Mehi River near Moree reached more than 10.6 m, similar to the height reached in 1976 floods. Approximately 300 homes in Moree were inundated, and 1600 people were evacuated.

The concern became from floodwaters from Queensland moving downstream to northern areas of New South Wales such as Mungindi, Walgett, Bourke, Collarenebri and Brewarrina.

On 9 February, heavy rains caused flash flooding across western Sydney and the Illawarra, with the SES receiving approximately 450 calls for assistance.

On 20 February a similar event occurred with flash flooding across Sydney and the Illawarra prompting more than 300 requests for assistance to the SES. Terry Hills recorded 61 mm in an hour and Peakhurst recorded 26 mm in just ten minutes. Other suburbs affected included Banksia, Rockdale, Padstow Heights, Sylvania, Five Dock and Rosebery.

Up to 8,000 people remained isolated for weeks in the north-west, receiving approximately 50 ton of daily deliveries such as medication, mail and food.

Heavy rains from the end of February to the beginning of March saw more than 75 per cent of New South Wales under water or threatened by floodwaters. Twenty-four hour rainfall totals to 9 am on 1 March reached up to 123 mm in Coolamon, 84 mm in Cootamundra, 83 mm in Broken Hill and widespread falls between 30 - 80 mm in the Illawarra district. Over 1700 people from the four towns of Bega, Eastgrove in Goulburn, Cooma and south-west Cowra were evacuated on 1-2 March.

Sydney's Warragamba Dam spilt at approx 6.53 pm on 2 March for the first time since 1998, causing authorities to cut power to 160 homes. The spillage prompted the evacuation of 1900 people from the Hawkesbury Nepean Valley area.
The town of Pooncarie in western New South Wales received approximately 174 mm of rain and Ivanhoe 154 mm for the 48 hours to 9 am on Thursday, breaking two-day rainfall records.

In Towamba approximately 367 people were isolated following the closure of the Princes Highway. The SES responded to more than 740 requests for help as the large, slow-moving trough set in.  Approximately 4600 people across the state were subject to evacuation orders and 2500 people were isolated, mostly on rural properties.

Approximately 9,000 people were evacuated from Wagga Wagga and a state of emergency was declared as the town's flood levee was tested by a peak of 10.6 m on 6 March, risking inundation of more than 3000 properties.

Evacuations continued throughout the first week of March with approximately 236 people door knocked in the Lachlan River area, 600 people ordered to evacuate in Griffith, and flood evacuation orders issued for Forbes, Flowerdale, Urana, Barellan, Yenda, North Wagga, Gillenbah and parts of Gumly Gumly. The town of Forbes was cut in three by floodwaters, inundating dozens of businesses and homes in the CBD.
More than 400,000 sandbags were distributed across New South Wales to protect communities from floodwaters.

The New South Wales Government declared 63 natural disaster zones during the February/March floods for the Albury, Balranald, Bathurst, Bega Valley, Berrigan, Bland Shire, Blacktown, Blayney, Bogan, Bombala, Boorowa, Broken Hill, Cobar, Cabonne, Carrathool, Central Darling, Conargo, Coolamon, Cooma-Monaro, Cootamundra, Corowa, Cowra, Forbes, Goulburn, Greater Hume, Griffith, Gundagai, Harden, Hawkesbury, The Hills, Hay, Jerilderie, Junee, Lachlan, Leeton, Lithgow, Lockhart, Mid-western, Murray, Murrumbidgee, Narrandera, Narromine, Oberon, Palerang, Parkes, Penrith, Queanbeyan, Shellharbour, Shoalhaven, Snowy River, Temora, Tumbarumba, Tumut, Mid Western Regional, Unincorporated Area of NSW, Upper Hunter, Upper Lachlan, Urana, Wagga Wagga, Weddin, Wentworth, Wollongong, Yass and Young local government areas.

Approximately 30 towns across the state's north-east were inundated, leaving 1000 properties isolated. Almost 2000 homes were flooded and more than 17,000 people requested emergency assistance.

On 12 March the Insurance Council of Australia stated that insurers had already received claims totalling more than $64 million from flood-affected homeowners in Victoria and New South Wales. Insurers received 8,200 claims across the declared catastrophe zone.
 
On 31 January one person drowned when they attempted to drive through floodwaters 1.6 m deep.

On 4 March one person died and two others were admitted to hospital with hypothermia and severe bruising after their four wheel drive was caught in a swollen causeway near Braidwood in the Southern Tablelands.

On 9 March one person was found dead in floodwaters north of Bourke, and their vehicle partially submerged in a causeway.

To date the Australian Government Disaster Recovery Payments total approximately $17,256,000 allocated to 14,834 claimants  affected in the northern part of the state and $29,991,000 was allocated to pay over 28,860 claimants affected by flood in the southern New South Wales region.

The Insurance Council of Australia estimated the 2012 damage at $108.2 million which incorporated figures for both New South Wales and Victoria.