A severe thunderstorm warning with large hailstones, noxious winds and strong winds issued rain was expected for parts of the Blue Mountains, Hawkesbury and Sydney areas.
The Bureau of Meteorology forecast shortly after 3 p.m. Monday that the heavy rain could lead to flash floods.
The thunderstorms were moving east and should hit Parramatta, Baulkham Hills, Blacktown, Fairfield, Horsley Park and Riverstone by afternoon.
The state rescue service advised people to move their cars under cover and away from trees, remove loose objects from their properties, and stay away from fallen power lines.
It also warned people not to walk or ride a bike through floods, and keep children and pets indoors.
A more general severe thunderstorm warning currently applies to Hunter, Metropolitan, Illawarra, South Coast, Central Plateaus, Southern Plateaus, Central Western Slopes and Plains, and parts of the mid-north coast, northwestern slopes and plains, southwestern slopes, Lower Western, Upper Western and Snowy Mountains districts.
Thunderstorms, Bureau of Meteorology, Sydney, severe thunderstorm warning, flood, severe weather
News – AU – Severe storm warning for the Sydney area