The Hunter is facing eerie warnings from meteorologists and emergency services a year on from a May drenching that caused widespread flooding and a major landslide that left homes uninhabitable.
Hunter residents awoke with parts of the region blanketed in fog on Wednesday and faced a bleak forecast for the days ahead.
The Bureau of Meteorology has issued a severe weather warning for parts of the Mid North Coast, Hunter North West Slopes and Plains and the Northern Tablelands
Isolated rainfall totals could exceed 100mm, dredging up memories of a wet end to autumn in 2025.
Widespread rainfall and thunderstorms are forecast through to Friday, with localised heavy rainfall and storms expected across much of the state.
A large upper trough is moving over NSW and Queensland and is likely to form a low-pressure system about coastal NSW during Thursday.
Daily rainfall totals of 20-40mm are likely, with heavy falls of 70-80mm possible locally from slow-moving thunderstorms.
Isolated falls could push 100mm.
The warnings come a year after the region was hit by a drenching that caused widespread flooding.
Between May 19 and 23 last year, a coastal trough and upper low combined with moist onshore winds to bring heavy rainfall to eastern NSW, particularly the northern regions of the Hunter and the Mid North Coast.
Five-day rainfall totals exceeded 400mm. Heavy falls and the sodden ground proved disastrous for residents in New Lambton as the largest residential landslip in Australian history, destabilised 16 homes at New Lambton.
Early estimates showed costs to restore the site could soar to more than $130 million.
From Wednesday, the focus areas of rainfall is forecast to shift into the northern inland and the northeast quarter, including the Mid North Coast, Hunter and extend to Greater Sydney and Illawarra.
The NSW State Emergency Service (SES) is urging communities across northern and eastern NSW to monitor conditions and understand their flood risk this week, with flash flooding and river rises possible as the severe weather impacts parts of the state.
NSW SES Assistant Commissioner Colin Malone said flash flooding was a risk, and can happen without much warning.
"We remind the community to steer clear of flood water. If you come across a flooded road, turn around and find an alternative route," he said.
"Our crews are well prepared to respond and have been put on standby across the state, but we're asking the community to do their bit and not take any unnecessary risks."
Prolonged rainfall may cause river level rises, and the NSW SES has issued a number of Advice warnings for flooding across the Hunter and parts of the mid-north coast.
Minor flooding is possible along the Paterson and Williams rivers overnight Thursday into Friday, and on the Manning and Gloucester, Goulburn and Hunter rivers as well as Wollombi Brook from Friday.
Assistant Commissioner Malone urged communities to stay up to date with the latest information and warnings.
"There is some uncertainty around the location of the heaviest falls, but NSW SES is working closely with the Bureau of Meteorology and will issue any warnings as required," he said.
"Download the Hazards Near Me app and set up a watch zone with your local area so you are alerted with the latest advice."
During the weekend, rain is expected to ease as the weather system moves offshore.
A hazardous surf warning is also in place for the Hunter coast.
Surf and swell conditions are expected to be hazardous for coastal activities such as rock fishing, boating, and swimming in the following areas.
