Late summer heat for New South Wales with parts of Sydney on track for 40C

New South Wales will swelter through an unusual burst of summer weather in March, with a heatwave expected to grip the state this week as temperatures in parts of Sydney reach close to 40C.

From Wednesday parts of NSW will experience multiple days in the low to mid 30s while other areas will reach the high 30s.

Narramore said the heat was being dragged across the state from central Australia and would linger across much of NSW until next week. It would probably break along the coast early next week and in inland areas in the middle of next week.

While it is normal to get bursts of heat during March, Narramore said it is unusual for the heat to last long.

The heat comes just over a week after NSW saw a record-breaking demand for electricity in March at 13,136MW, as Sydney recorded its third-hottest day on record for the month.

The Australian Energy Market Operator expected electricity consumption to peak at 11,700MW at 6pm on Thursday and said there was enough supply to meet demand.

The wind was likely to pick up across the state alongside the heat, Narramore said, and cautioned people to be mindful of the increased bushfire risk.

The bureau also confirmed that the La Niña that has brought much of the rain to the east coast is over.

In a statement, the bureau said oceanic and atmospheric indicators have returned to neutral levels and are likely to remain until autumn.

But they have also switched to an El Niño watch, saying that there are some signs the weather event could form this year.

The drier-than-usual conditions could be detrimental to the coming bushfire season, with firefighters already battling blazes in NSW.

A spokesperson for the RFS said grassfires could start easily and spread rapidly under the forecasted dry and windy conditions.