Dramatic backlit mammatus clouds over Sydney.
© Jemma Wlasichuck, Facebook
Dramatic backlit mammatus clouds over Sydney.
An unusual cloud formation has covered skies in parts of Sydney as NSW was again hit by wild weather.

Social media has lit up after an unusual cloud formation was seen around Sydney on Wednesday.

Known as mammatus clouds, the formation is most often associated with thunderstorms.

"Never seen anything like it," one Twitter user wrote.

The Bureau of Meteorology (BOM) issued several severe thunderstorm warnings around the state on Wednesday.

"Severe thunderstorms are likely to produce damaging winds in the warning area over the next several hours. Locations which may be affected include Yass, Parkes, Condobolin, Young, West Wyalong and Cootamundra," BOM material said at 8pm AEST.

"Severe thunderstorms are no longer occurring in the Hunter, Metropolitan, Illawarra, South Coast, Upper Western and Snowy Mountains districts and the warning for these districts is CANCELLED."

The BOM said 3cm hail was reported at Blackheath at 3:30pm AEST, with social media users sharing videos.

It comes only two weeks after Sydney was hit by a storm that the Insurance Council of Australia called "catastrophic", incurring more than $125 million in damage.