Sydney again faces severe thunderstorms as heavy rain hits East ...

Heavy rain soaked eastern, central and northern parts of New South Wales yesterday and prompted flash flooding warnings.

Sydney was smashed with up to 80mm while Sydney Airport recorded its highest rain in two months of 39mm in the 24 hours to 9am today, according to Weatherzone.

About 864,000 lightning strikes were recorded in the city and as far as the Queensland and Victorian borders.

Severe weather conditions are continuing today thanks to a coastal trough north of Wollongong.

Canterbury in the city's west has already been hit with 32.6mm of rainfall since 9am while Sydney Airport has faced 29.6mm.

The Bureau of Meteorology has issued a severe thunderstorm warning for the Sydney and Illawarra areas this afternoon, with fears of potential flash flooding to come.

Wollongong, Campbelltown, Bulli, Port Kembla, Albion Park and Kiama are forecast to be hit the worst.

Residents are urged to move their cars under cover and away from trees, secure loose items around their homes and keep at least eight metres away from fallen power lines.

In instances of flash flooding, they were warned to seek high ground and dial Triple Zero.

Sydney is anticipated to see wet weather for the remainder of this week until conditions finally clear by the weekend.