Forecast localised heavy rainfall associated with the storms could cause flash flooding in the Sydney, Illawarra, Hunter, Southern Highlands and the Central West throughout the weekend. The Bureau of Meteorology has also forecast damaging wind gusts in eastern areas until Saturday.
On Sunday and Monday, severe thunderstorms are likely to persist along central and northern half of the coast and northwest, with heavier falls possible closer to the Queensland border. There is a risk of strong and damaging wind gusts and large and powerful surf over the Northern Rivers and Lord Howe Island.
NSW SES Assistant Commissioner Colin Malone said conditions could change quickly if forecast thunderstorms brought heavy rainfall.
"We are working with the Bureau of Meteorology to monitor the development of severe storms and we're prepared to issue any warnings as required," Assistant Commissioner Malone said.
"The best thing that you can do is have the Hazards Near Me app downloaded and set up a watch zone for your area, so you are alerted with the latest warnings and advice."
Assistant Commissioner Malone urged residents to stay vigilant as storms can develop quickly and cause flash flooding without much warning.
"We've seen over the past week how quickly rainfall can intensify and cover roads and we'd like to remind everyone to steer clear of floodwater," he said.
"If you come across a flooded road, turn around and find an alternative route or replan your travel for another day."
In the Far West, NSW SES continues to respond to flash flooding and resupply requests after recent storms cut off low-lying roads and river crossings and isolated rural properties and homesteads.
Teams in remote Western NSW have responded to five flood rescues in recent day for people driving into floodwater. The Barrier Highway remains closed and impacted by floodwaters.
Assistant Commissioner Malone said crews are on standby across the state and prepared to respond to any impacts of severe weather but urged communities to be prepared too.
"You can prepare your homes and properties ahead of storms by securing loose outdoor items, trimming overhanging branches and clearing your gutters and downpipes," he said.
Conditions are forecast to ease from Tuesday, with another bout of thunderstorms possible across the state at the end of next week.
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).
