Breathtaking images have been captured of a huge storm known as a shelf cloud which formed off Sydney's Bondi Beach.
Many tourists and residents posted pictures of the phenomenon, dubbed a "cloud tsunami", on social media.
The low-hanging cloud formation prompted warnings about large hailstones, heavy rainfall and strong winds.
People were told to stay away from power lines, trees and drains.
Forecasters said the instability was caused by moist air mixing with cooler winds.
@7NewsSydney storm coming across #coogee pic.twitter.com/j4zoGXi2Rw
— Andrew Price (@pricey43) November 6, 2015
A similar cloud system caused rush-hour flooding when it moved over Sydney in March 2014.
Photographer Nick Moir, of the Sydney Morning Herald, has been following the clouds.
"Shelf clouds are pretty common but to get them so big and coming right up the coast of Sydney is not that common - you get a couple a year" he said.
"This is a pretty significant one, plus it's been a warm day, a lot of people are out - particularly at Bondi - and this huge mammoth storm just started rolling up the coast and of course social media went atomic".
Mr Moir said the system had been moving through the region over the past two or three days, with a number of tornadoes and heavy rain being reported with it.
"Generally, with severe storms, often flash flooding is actually the real killer - not so much the tornadoes or massive hail".
"It has moved through Sydney and is moving up the coast at the moment".
"It's moving very rapidly out to the ocean so by tomorrow (Saturday) things should have calmed down" he added.
#storm in #Sydney forms large shelfcloud #sculpturebythesea pic.twitter.com/79PK9bBl4E
— Nick Moir (@nampix) November 6, 2015
Watch a time lapse video of the phenomenon below:
