Flash flooding in Sydney after rain deluge

A torrential downpour in Sydney has led to flash flooding in several suburbs, with more to come. (AAP)

A torrential downpour has drenched Sydney and other parts of NSW with the rain expected to last throughout the week.

Flash floods have impacted many towns and city roads, the SES said on Tuesday afternoon.

Rescue crews have attended to at least 15 flood rescues across Sydney and the Central Coast with 450 call-outs statewide.

"We are imploring you with 15 flood rescues in inner Sydney and up at the Central Coast, that's too many... Please don't drive through floodwater," the SES said.

Sydney and some NSW regions are being drenched, with a warning a severe thunderstorm is on the way. (AAP)

Flash flooding inundated various Sydney suburbs with Marrickville in the inner west recording at least 110mm.

Wyong in the Central Coast was battered by 80mm in 45 minutes only.

The Bureau of Meteorology said the immediate threat of severe thunderstorms has passed.

Weatherzone, a weather tracking service, warned "large areas of eastern Australia will be stuck in a stormy weather pattern...that could see several hundred millimetres of rain this week".