Widespread rainfall and thunderstorms are forecast through to Friday, with localised heavy rainfall and storms expected across much of the state. From today, the focus areas of rainfall is forecast to shift into northern inland and the northeast quarter including the Mid North Coast, Hunter and extend to Greater Sydney and Illawarra.
Daily rainfall totals of 20-40mm are likely, with locally heavy falls of 70-80mm possible with slow-moving thunderstorms.
NSW SES Assistant Commissioner Colin Malone said flash flooding was a risk with thunderstorms and can happen quickly, 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," Assistant Commissioner Malone 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.
If you need assistance during storms and floods, call the NSW SES on 132 500. In a life-threatening emergency, always call Triple Zero (000).
