Millions of Aussies are at risk of enduring rolling blackouts this week, amid a heatwave sweeping through NSW and unexpected coal outages across the state.

A blackout risk continues in New South Wales on Wednesday as Aussies brace for what is expected to be the peak of the heatwave.

Millions of Aussies could lose power this week as a heatwave grips the country - amid warnings wet and wild weather will smash 'every state and territory'. A total of 347 sites suffered blackouts during an unplanned outage in Sydney's CBD at 3pm on Tuesday,

Millions of residents across NSW have suffered blackouts as the heatwave continues to grip the nation, with temperatures expected to tip as high as 39C across parts of Sydney on Wednesday, while sheets of rain and thunderstorms continues to blanket areas of Victoria.

Australia's most populous state is facing an elevated risk of blackouts amid a forecast looming heatwave, the Australian Energy Market Operator (AEMO) warned on Monday.