WATCH: Wild thunderstorm strikes Sydney

A SEVERE thunderstorm has left residents counting the cost of damages after powerful winds, driving rain and hail lashed regions surrounding Sydney.

The powerful storm caused flash flooding and cut power to almost 1000 homes across the Blue Mountains, Central Coastal, and Sydney's northern and western suburbs.

In video of the storm, driving rain and pea-sized hail hammers a backyard in north-western Sydney.

The conditions caught out a 61-year-old after the car she was driving became trapped in floodwaters. She was travelling with two children aged five and nine.

Police said the woman was issued with an infringement notice.

The storm was déjà vu for residents who are still mopping up from last week's wild weather, and with the forecast predicting even more extreme weather, Sydney-siders might have to get used to a further battering.