Severe heatwave to strike Australia today

Blackout warnings for households along the east coast have been downgraded after coal plant operators pulled planned outages during a predicted heatwave.

The Australian Energy Market Operator issued a warning on Monday about blackout risks in NSW and Queensland on Tuesday afternoon and Wednesday, when temperatures could soar to 40C in parts of Sydney.

Increased air-conditioning use and generator repairs at three NSW coal-fired power plants threaten to shut down the grid in some areas.

'High temperatures and strong electricity demand, combined with some generation outages, are causing tight electricity supply forecasts in NSW tomorrow and Wednesday afternoon,' a spokesperson for the operator said. 

The energy operator downgraded the warnings late on Monday afternoon.

'The previously forecast Lack of Reserve Level 3 has been downgraded to a less critical Lack of Reserve Level 2,' a spokesperson said.

'This improvement is largely due to the cancellation of transmission outages in the region.'

The market operator said it would take 'all necessary measures' to boost supply if forecasts deteriorated again.

Earlier on Monday, energy companies were asked to switch off big electricity users and boost supply across the state.

'AEMO has alerted the energy industry and is working with power station operators and transmission businesses to boost electricity availability,' a spokesperson said.

'If a market response remains inadequate, AEMO will take actions available to maintain supply.'

NSW Energy Minister Penny Sharpe said people should look out for each other during the heat spike.

She said the government was keeping an eye out for any energy-supply problems.

'You should drink water, you should check in on neighbours and you should think about whether you need to walk out in the middle of the day in the beating hot sun,' she said.

'Do you really need to have every single light on in the house ... do you need to have your air conditioning down at 19 degrees? You don't.'

The Bureau of Meteorology on Monday enacted a heatwave warning in NSW and Queensland due to last until midweek.

The temperature in the Sydney city centre is forecast to peak at 33C on Wednesday and could reach 40C in the northwest suburbs.

The heatwave is predicted to end on  Thursday and Friday, with rainy and stormy conditions likely. 

The predictions follow a week of soaring temperatures in Victoria, where parts of Melbourne reached 37C - well above the November average.