Millions of people along Australia’s east coast should keep their brollies handy this week as a prolonged drenching begins.

Forecasters say falls of 30mm to 70mm are expected along the coastal fringes of NSW and Queensland, but some isolated areas may record up to 100mm.

The unsettled weather has triggered a hazardous surf warning by the Bureau of Meteorology for waters on the K’gari coast, Sunshine Coast and Gold Coast.

Looking ahead, the rain will stretch from the South Coast of NSW to Queensland’s northern goldfields and is forecast to be heaviest on Thursday and Friday.

There will also be the likelihood of thunderstorms in southern Queensland and north-east NSW on those days.

Relief from the stormy conditions is expected by Saturday when the low-pressure system moves east towards New Zealand.

But it may only be brief because forecasters say there is the chance of a new trough building bringing more wet weather to the east coast.