The Bureau of Meteorology (BOM) has issued a severe warning for Newcastle and the Hunter.
According to the BOM, thunderstorms are likely to produce large hailstones and damaging winds in the region over the next several hours.
Locations which may be affected include Newcastle, Gosford, Cessnock, Maitland, Mudgee and Dubbo.
In the event of severe storm weather, the State Emergency Service (SES) advises that people move cars from away from trees; secure loose items around the house, yard and balcony; and stay at least 8 metres from fallen power lines or potentially energised objects like fences.
Residents can report fallen power lines to the energy provider shown on their power bill, including Ausgrid (131 388), Endeavour Energy (131 003), Essential Energy (132 080) or Evoenergy (131 093).
It is safest to stay away from creeks and storm drains and to refrain from walking, riding or driving through flood water.
For emergency help in NSW floods and storms, contact the SES on 132 500.
While you're with us, did you know the Newcastle Herald offers breaking news alerts, daily email newsletters and more? Keep up to date with all the local news - sign up here