Australians baking in an extraordinary heatwave could face yet more grief, as power problems threaten air conditioners and fans.

On Friday, NSW avoided load shedding of households in part by asking Tomago Aluminium, the country's biggest aluminium smelter, to reduce power output by about 300 megawatts. That was roughly the shortage that prompted blackouts to about 90,000 households on Wednesday evening in South Australia.

The smelter was asked to prepare to cut back power usage for a second day on Saturday.

MARK KOLBE/GETTY IMAGES Grabbing shade at Lady Robinsons Beach on Botany Bay.

During Friday evening, wholesale power prices in NSW peaked at their maximum level of $14,000 per megawatt-hour. Matt Howell, the chief executive of Tomago Aluminium, likened the price jump to turning up "at your local BP service station and paying $460 per litre of petrol".

READ MORE: Sydney braces for catastrophic record-breaking heatwave

MARK KOLBE/GETTY IMAGES Australian Energy Market Operator has warned of possible power shortages due to increased demand.

The situation's not getting better either, with health authorities issuing an air pollution alert for increased levels of ozone in the atmosphere in Sydney, which is likely to affect residents with respiratory problems.

Sydney's air quality is forecast to be poor throughout Saturday, as the mercury climbs to a forecast top of 39 degrees in the city and a sweltering 46 degrees in Penrith and Richmond. Penrith is a chance of notching up its hottest ever day, a record which presently stands at 46.5 degrees.

The abnormal heat could push the mercury to the state's hottest overall temperature on record for February on Saturday, reaching about eight degrees above normal.

MARK KOLBE/GETTY IMAGES Kurt Tippett of the AFL team the Sydney Swans cools down in front of the misting fans to combat the heat during a game.

In the state's west, the small township of Ivanhoe, population 200, is tipped to reach a maximum of 48 degrees on Saturday, while Menindee, Bourke and Wilcannia are each forecast to hit a top of 47 degrees.

On Friday, Hay Airport reached 47.4 degrees, making it the third-hottest temperature recorded in February for NSW - a high mark that might be bettered as soon as Saturday.

OZONE WARNING

FAIRFAX Sydney residents tried everything to stay cool on Friday.

Dr Ben Scalley, from NSW Health, urged people with respiratory conditions in Sydney to take precautions on Saturday due to high ozone pollution, caused by car exhaust and industrial fumes. Ozone pollution is particularly bad on hot, still days, he said.

"Parents are advised to limit outside play for children with asthma," Dr Scalley said.



"Ozone levels reach their peak around 7pm ... and tend to be lowest in the morning, so it's best to plan outdoor play in the morning when the day is cooler."

He urged asthma sufferers to follow their asthma action plans and take their relieving medication where necessary. If symptoms get worse, those affected should seek medical advice.

NSW HEATS UP

On the weather front, NSW could average eight degrees above average - recording about 43 degrees - at the peak of the heat.

The current record for February is 41.99 degrees. Reaching the all-time high would be a bit tougher - that figure stands at 44.06 degrees, set on January 14, 1939.

"For NSW, the area coverage of the heat is extremely rare, comparable with events such as the 1939 heatwave that were associated with the Black Friday bushfires in Victoria," Karl Braganza, head of climate monitoring at the Bureau of Meteorology, said, adding that the current record February day for the state was set in 2004.

CATASTROPHIC FIRE CONDITIONS FORECAST

Total fire bans are also in place across NSW on Saturday, with fire danger reaching "severe" levels in the Hunter and four other inland regions of the state. For Sydney, the threat is deemed "very high".

Rob Rogers, the Rural Fire Service (RFS) Deputy Commissioner, said "catastrophic" fire ratings were likely for parts of NSW, including the Hunter, on Sunday. Such a threat level has been issued only once before in NSW - in 2013 - since national standardised ratings were introduced in 2009.

On Saturday, he offered a blunt message to those considering visiting fire-prone areas: don't go.

"Go to the beach instead, do something else, particularly those people who may be thinking about camping. Plan it for another time," he said.

He said firefighters were expecting a particularly tough five-hour period on Sunday, before a southerly change swept through on Sunday evening and into Monday morning.

Saturday's top of 39 degrees, would make it Sydney's 11th day above 35 degrees this summer if achieved, extending the record broken on Friday.