Records tumbled in New South Wales on Friday as sweltering heat hit the east coast, but authorities warn the weekend could be worse.
The heatwave, which is expected to continue until Sunday, saw Sydney break a 121-year-old heat record for the number of summer days above 35C.
As of Friday afternoon, Observatory Hill had exceeded 35 degrees for the tenth time this summer (up to 37.2 degrees as of 2.49pm), breaking the previous record of nine days set in 1895/96.
READ MORE: Sydney has just broken a 121-year-old heat record
And the state's not out of the woods yet, with the Bureau of Meteorology forecasting the hottest February day on record this weekend.
Firefighters have been warned of potentially catastrophic fire conditions. The last time conditions were this dangerous was in 2013.
Demand on the state's power network reached unprecedented levels as temperatures on Friday soared to highs of 45C in western Sydney and 47C in the western Riverina town of Hay.
Earlier, energy minister Don Harwin urged residents to take steps to reduce their electricity usage as demand came close to exceeding supply.
The Australian Energy Market Operator (AEMO) has since downgraded the forecast shortfall, reducing the potential need for rolling blackouts.
A shortfall in supply risks the electricity network becoming "unstable" creating the need for "localised load shedding to rebalance the power system", according to the AEMO.
Up to 90,000 homes and businesses were deliberately blacked out in South Australia on Wednesday night in order to protect supply.
In New South Wales, the decision of where to cut power lies with the three energy providers Ausgrid, Essential Energy and Endeavour Energy.
If they receive notice from TransGrid that the system is overloaded they begin load shedding based on the scale of the power shortfall. The locations earmarked for interruptions are not released to the public.
Residents can reduce energy use during the late afternoon peak by turning up their air-conditioning to 26C, adjusting fridge temperatures, switching off unused electrical appliances and turning off lights.
The extreme weather hitting New South Wales, Queensland and Victoria has emergency services on standby and authorities pleading with the community to be vigilant.
All three states can expect extremely hot conditions on Saturday and Sunday with the mercury to climb well beyond 40C in many locations.
Victorians haven't been spared from the effects of the heatwave with temperatures expected to sit in the low 40s in northern parts of the state on Saturday before cooling down on Sunday.
Conditions are set to be brutal also in parts of Queensland, with the mercury forecast to reach 46C in several southwest towns including Birdsville, which could smash its February heat record of 46.2C on Sunday and possibly break the Queensland record of 46.5C.
Queensland authorities issued warnings about dehydration after three school students were hospitalised north of Brisbane suffering heat-related problems on Friday.
In New South Wales, a state-wide total fire ban is in place for Saturday and Sunday, with Rural Fire Service Commissioner Shane Fitzsimmons warning the following three days will be very difficult for firefighters as temperatures rise to above 40C.
The state's northwest will cop the burnt of the extreme heat with Wilcannia, Ivanhoe, Bourke and Menindee all tipped to reach 47C on Saturday.
In the Hunter region, Singleton and Cessnock are predicted to reach 46C on Saturday and 43C on Sunday.
Mr Fitzsimmons warned of a potential "catastrophic" fire danger warning on Sunday "largely around the Hunter, from the coast, mid-north coast, out through the Central Tablelands, the top end of the greater Sydney region and out to the central west".
He said people should have their bushfire survival plan ready.
"We need everybody in these most-at-risk areas to do their part," he said.
Sydney will get no relief over the weekend with high 30s and low 40s forecast across the city.
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The state's Forestry Corporation has closed all forests between Sydney and Kempsey in the state's north, along with forests in the Pilliga region and the Talleganda State Forest on the Southern Tablelands on Saturday, with the situation to be reassessed for Sunday.
Saturday's Randwick races have been postponed to Monday due to concerns about the welfare of horses and riders.
Newcastle's A-League soccer match against Melbourne Victory has also been postponed until Monday, while Football NSW has cancelled all Saturday trial games for under-18s and below and shifted under-20s and first grade trials to evening start times.
Three NRL trial matches will however go ahead on Saturday evening, as will the Sheffield Shield clash between New South Wales and Queensland. Cricket NSW has cancelled all grades of Premier Cricket, while most school and children's sport has been cancelled.
With many people heading to waterways to cool off in the heat, parents are being urged to keep an eye on children following a tragic summer of drownings.
Health experts are reminding people to stay hydrated, wear sunscreen and look out for people most at risk, while New South Wales clubs say they will provide water and respite for vulnerable people.
On Thursday, NSW Police activated the Heatwave Action Plan, which will remain in place until Sunday.
NSW Health has advised people to stay hydrated, limit physical activity, avoid alcohol and sugary drinks and try to stay out of the sun during the hottest part of the day.
Police advised residents to stay in air-conditioned buildings and take care of those most vulnerable, especially the elderly and those who live alone.
Authorities also reissued a warning for motorists not to leave children, pets or the elderly in hot cars.
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