The summer of storms continues for NSW with large swathes of the state - including the western Sydney metro region - facing another bout of thundery weather.

The Bureau of Meteorology issued a severe thunderstorm warning for western parts of the metropolitan area, the Illawarra and a region stretching from Goulburn to Tibooburra in the state's far north-west.

A mammatus cloud forms ahead of a thunderstorm tracking north east over Blaxland in Sydney’s west on Wednesday afternoon. Credit:Wolter Peeters

The alert said the storms were "likely to produce heavy rainfall that may lead to flash flooding, damaging winds and large, possibly giant hailstones over the next several hours".

David Wilke, a bureau duty forecaster, said Camden in Sydney's south was one area in the line of the storms.