The Bureau of Meteorology has issued a severe thunderstorm warning for damaging winds, large hailstones and heavy rainfall.
The Shoalhaven and Southern Highlands could be impacted.
The State Emergency Service advises that people should:
* Move your car under cover or away from trees.
* Secure or put away loose items around your house, yard and balcony.
* Keep at least 8 metres away from fallen power lines or objects that may be energised, such as fences.
* Report fallen power lines to either Ausgrid (131 388), Endeavour Energy (131 003), Essential Energy (132 080) or Evoenergy (131 093) as shown on your power bill.
* Trees that have been damaged by fire are likely to be more unstable and more likely to fall.
* Keep clear of creeks and storm drains.
* Don't walk, ride your bike or drive through flood water.
* If you are trapped by flash flooding, seek refuge in the highest available place and ring 000 if you need rescue.
* Be aware that run-off from rainfall in fire affected areas may behave differently and be more rapid. It may also contain debris such as ash, soil, trees and rocks.
* After bushfires, heavy rain and the loss of foliage can make the ground soft and heavy, leading to a greater chance of landslides.
* Unplug computers and appliances.
* Avoid using the phone during the storm.
* Stay indoors away from windows, and keep children and pets indoors as well.
* Stay vigilant and monitor conditions. Note that the landscape may have changed following bushfires.
* For emergency help in floods and storms, ring the SES (NSW and ACT) on 132 500.
Image: Bureau of Meteorology