Emergency services are bracing for what is predicted to be one of the hottest days of the year as a dangerous "blast furnace" moves across Australia.
Large parts of southeast Australia are set to swelter through the extreme heat today, with dry, gusty north-westerly winds sending hot air from Central Australia to New South Wales, delivering the searing heat.
Sunday is expected to be the "first extreme heat day of the year" across New South Wales and various parts of Australia, reports News.com.au.
Ambulance Victoria state health commander Paul Holman described the conditions "like a blast furnace".
Authorities say the hot conditions are not expected to ease until Tuesday.
"The real issue is that we're not going to see a relief in NSW until early next week, so we're going to see sustained heat over the days and the nights," Deputy Commissioner Catherine Burn said.
A Bureau of Meteorology spokesperson told ABC News this morning that "a weak change should drop temperatures a little bit this evening, but it's quite a short lived change and it will get warm again tomorrow ... it shouldn't get as hot, but western parts of Sydney should see 40C tomorrow again," the spokesperson said.
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• New South Wales:
Residents have been warned of a rise in ozone pollution and fire dangers as temperatures soar into the mid-40s in parts of New South Wales.
Temperatures are forecast to hit 40C in Sydney's CBD. In the western suburbs, the mercury will soar to 45C in Penrith.
Sydneysiders won't get any real relief until Wednesday, when the mercury will reach just 25 degrees with a shower or two also on the cards.
• South Australia:
South Australia is expected to be "substantially cooler" than yesterday, with temperatures expected to peak around 28 degrees.
Thursday will reach a weekly high of 32 degrees in Adelaide with a shower also possible.
• Tasmania:
The same is said for Tasmania after a cold front crossed the state last night. Temperatures are expected to drop after a high yesterday of 35.8 degrees, with cool and mostly dry conditions.
The hottest day of the week in Hobart will be Thursday when it reaches 29 degrees.
• Queensland:
In Queensland, temperatures are forecast for a high of 32 degrees for the rest of the week.
• Western Australia:
While Perth is less affected by the heatwave, temperatures are forecast for 31 degrees, reaching as high as 33 degrees by Tuesday.
• Victoria:
It's a different story entirely in Melbourne. The day will be partly cloudy, and the city is tipped to hit a high of just 22 degrees today.
Temperatures will hover around the low to mid-20s in Melbourne for most of the week, but will reach 34 degrees on Thursday.
• Northern Territory:
It will reach a high of just 30 degrees in Darwin today, with rain and storms likely. Showers and temperatures in the low 30s will continue for the week ahead.
• ACT:
Canberra will be hot and sunny today with a high of 39 degrees. There's some relief in store, however, with temperatures dropping to 30 degrees tomorrow with a chance of showers.
A severe fire danger rating was issued for the greater Sydney region on Sunday while much of the rest of the state has a "very high" rating. Total fire bans are in place for Sydney and the Hunter Region.
Extreme heat and fire risk warnings have been issued for Victoria, South Australia, New South Wales and Tasmania.
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New South Wales, Victoria and South Australia bore the brunt of the heatwave yesterday with extreme conditions in Melbourne sparking a large bushfire.
It comes as residents in South Australia described a "wall of flames" that threatened properties overnight in Keith, a small farming town in the southeast of South Australia.
The Advertiser described a "day of catastrophic conditions" as the flames tore through more than 800ha, destroying property and valuable grain crops.
A Country Fire Service crew escaped serious injury when they were trapped inside their truck as the inferno "burnt over", while dozens of their colleagues heroically saved multiple properties.
The CFS battled more than 40 fires across the state on Saturday — 19 in rural areas.
In Melbourne, a team of 300 firefighters, 50 trucks and three helicopters worked furiously to save homes in Carrum Downs from a bushfire which has now been brought under control.
"I saw one small fire then it just took off. It was scary," Ray Torpy, told the Herald Sun.
The NSW Rural Fire Service is warning residents to prepare their bushfire plans. If people are considering leaving their homes they should "leave early", the RFS said.
NSW Health has warned people to drink plenty of water and limit their time outdoors because of a rise in ozone pollution as a result of the hot, still weather.
Sydney is forecast to have poor air quality on Sunday which can especially affect people with asthma and chronic obstructive pulmonary disease.
"Ozone levels are higher outdoors than indoors, so limiting time outside during the heat of the day and in the evening would help people to keep cool and to limit their exposure to ozone pollution," Environmental health director Dr Ben Scalley said in a statement on Saturday.
Dr Scalley also warned of the dangers of a heatwave which put strain on the body, can cause dehydration, heat exhaustion and heat stroke.
NSW Police Deputy Commissioner Catherine Burn on Saturday revealed the state's heatwave plan had been activated to ensure a co-ordinated response from emergency services.
"We know over the next two or three days we're going to experience severe to extreme heat conditions throughout NSW," she said before reminding people it was an offence to leave children or pets in vehicles.
"Cars become a furnace very, very quickly in this type of heat." Surf Life Saving NSW has implored people heading to the beach to take care given there have been 10 drownings since the beginning of December.
A 48-year-old is fighting for his life after he was found face down in the water at Sandon Point Beach on Saturday.
In a separate incident, a 35-year-old man was taken to hospital in a stable condition after being pulled semiconscious from the Hawkesbury River at Lower Portland.
- Additional reporting AAP
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