Southern Sydney resembled a disaster zone on Wednesday after the most destructive winds recorded in NSW history lifted roofs off houses, brought down power lines and trees and left more than 20,000 homes and businesses without power.

The first of multiple severe thunderstorms hit Sydney just after 10:30am, when a tornado-like event ripped through the Sutherland shire region.

The storm's brunt was felt in southern beachside suburb of Kurnell, which was lashed with record breaking winds of 213km/h, heavy rain and golf-ball sized hail. A trail of destruction confronted residents and State Emergency Service workers on Wednesday afternoon as they worked to remove debris and cut down trees that had fallen across roads, yards and cars.