CANBERRA, Jan. 25 (Xinhua) -- Thousands of Australians have been left without power as the nation swelters through its worst heatwave since records began.

The temperature in Adelaide, capital of South Australia (SA), hit 46.6 degrees centigrade on Thursday afternoon, the highest temperature recorded in the city since records began in 1939.

It was one of 28 suburbs and towns that experienced their hottest day on record on Thursday. In Port Augusta, 310 km north of Adelaide, temperatures soared to 49.5 degrees centigrade while in Tarcoola, a further 413 km east, the temperature record was broken for the second time in nine days.

South Australia's energy grid has been under pressure to meet peak energy demand since the state closed all of its coal-fired power generators, instead promoting renewable sources.

Paul Roberts, spokesman for SA Power Networks, said that the blackouts were triggered by blown fuses rather than an energy supply shortfall.

"Like humans, electrical equipment's capacity to work reduces as it gets hotter," he told News Corp Australia on Friday.

"Once equipment gets too hot protection devices will operate to prevent catastrophic damage," he said.

"Our transformers have fuses that will respond to the transformer reaching load capacity, which reduces as the equipment heats. Much better the fuses operate than the transformer has a catastrophic failure," he said.

"With the combination of record temperatures and potentially record loads we have been in unprecedented territory today," he added.

In Melbourne, capital of Victoria, the Bureau of Meteorology (BOM) forecast that the temperature would hit 44 degrees centigrade on Friday, which would make it the hottest day in the city since Black Saturday, Feb. 7, 2009, when the worst bushfires in Australian history began.

A cool change was expected to hit the city at 3:00 p.m. local time, reducing temperatures by 15 degrees centigrade in 20 minutes.

The Australian Energy Market Operator (AEMO) said it was not expecting blackouts in Victoria despite increased demand for electricity.

"We're not expecting blackouts. We're not yet expecting to call our reserves," Aubrey Zibelman, chief executive of AEMO, told reporters.

Alice Springs, the largest city in Central Australia, was warned to brace for its 14th consecutive day with temperatures above 42 degrees centigrade on Friday. The city has recorded more days over 45 degrees centigrade in one week than it did in the previous 76 years combined.

The extreme heatwave has exacerbated conditions for firefighters battling fires near Alice Springs that have already ravaged 30,000 hectares of bushland.

"That's because a lot of the heat that has been driving this heatwave has been originating from Northern Australia, particularly Northern Western Australia, and then we see weather systems come through and capture that heat and push it form Central and Southern Australia," Billy Lynch from the Alice Springs BOM said.