Several of Sydney's beaches were deserted on Wednesday after storms caused major pollution across the eastern suburbs and the northern beaches.
The NSW government has issued warnings about debris and faecal contamination for many parts of Sydney's coast, encouraging members of the public not to go swimming.
North Curl Curl and Tamarama beaches were officially closed due to the likely possibility of pollution and dangerous surf conditions, while warnings to avoid swimming were issued for many other popular beaches, including Manly, Collaroy, Bondi, Bronte and Coogee beach.
Only 4 out of 62 beaches in the Sydney and Pittwater regions were reported to have no pollution in the water.
The Bureau of Meteorology issued a severe thunderstorm warning just after 6pm on Tuesday for the Blue Mountains, Hawkesbury region, Greater Wollongong, Sydney, Wollondilly and Wingecarribee???.
The storms caused 40.5 millimetres of rainfall, 20 to 30km/h winds and 22,000 lightning strikes, which caused 11,000 homes and businesses to lose power across Sydney.
Endeavour Energy said it was "bringing in extra crews to assist with restoration efforts, but asked customers to be patient due to the extensive damages to the network".
By Wednesday morning, power had been restored to all but 2100 customers.
The NSW Office of Environment & Heritage said on its website that "the most obvious signs of stormwater pollution are water discolouration as well as debris in the water and on the tide line".
The possible diseases a person can be exposed to when swimming in polluted waters include gastroenteritis, ear, nose and throat infection and in more serious instances, deep tissue or blood infections.
More storms are expected over the coming week with as much as 20 millimetres of rain expected in Penrith on Saturday, the bureau said.
