A severe thunderstorm warning for heavy rain, damaging winds and large hail has been issued for parts of NSW as Sydney also braces for wild weather in a big change from the state's scorching heatwave.

Severe Thunderstorm Warnings will be issued if the storms are expected to produce any of the following: Damaging wind gusts (90 km/h or more) Large hail (2cm diameter or more) Very heavy rainfall ...

Severe thunderstorms can produce damaging wind gusts, large hail, tornadoes and heavy rain which may cause flash flooding and these phenomena can all cause significant damage. Most thunderstorms do ...