Despite all the warning to take care and keep cool, there were plenty of people overcome by heat.

For a 70-year-old man who was already ill, today's heatwave was too much, and he suffered a fatal heart attack in Sydney's Northmead.

The New South Wales paramedics spent the day on high alert due to the furnace-like conditions.

• Coping with Australia's heatwave
• Tasmanians stranded by bushfires
• Australia's wild weather boom

And as temperatures climbed, more people succumbed to the heat, including three teenage climbers on the Harbour Bridge. A fifteen-year-old boy collapsed unconscious.

According to Kevin McSweeney, Inspector with the NSW Paramedics, "the calls we get are of people in distress. When we get there they're obviously very flustered, sometimes they're sweating a lot and sometimes they've gone past that stage and aren't sweating, which generally can be worse."

McSweeney says "it's a matter of cooling them down, getting them rehydrated, and sometimes (you) give them fluid intravenously and hopefully get them back on track."

Tips to cope with the heatwave

In New South Wales today the Ambulance Service responded to hundreds of calls, but the mercury soared right across the country.

In New South Wales Fowlers Gap and Wilcannia were the hottest spots, reaching 44.8 degrees.

In Queensland Birdsville hit 44 degrees, while in Victoria Mildura sizzled at 37.9.

More stories from reporter James Thomas

Leonora in WA reached 47.7 degrees, while Tasmania was cooler today - Friendly Beaches was the hottest at 31 degrees.

Canberra sweltered at 37.7 and it reached 46 degrees in Wulungurry and Ulara in the Northern Territory.

In South Australia the town of Oodnadatta - famous for being Australia's hottest spot, lived up to its reputation, reaching 48.2 degrees.

New colours on the Bureau of Meteorology chart show temperatures reaching the 50s.

Oodnadatta has experienced ten days straight of temperatures over 40 degrees, though locals say you never do get used to the heat.

"Most people just stay indoors as much as possible. If you want to go out, you get up early and do your business, go around in the morning and just stay indoors in the afternoon," Linnie Plahta, owner of Oodnadatta's Pink Roadhouse said.

It's hard to imagine that temperatures like those of today could well be a sign of things to come, but weather forecasters and climate scientists say that this is climate change in action.

Check out tomorrow's forecast with Yahoo!7 Weather

Dr Mark Stafford-Smith, a scientist with the CSIRO, says you can't blame climate change for one heatwave, but you can for a series of them.

"Each decade has been warmer than the one before, so that's the average temperature steadily rising, and then what we're seeing within that is that the extreme hot days are occurring more and more frequently," Dr Stafford-Smith said.

"It's pretty clear that the general warming of the atmosphere, the general increasing global temperature is caused by human impact: the amount of carbon dioxide and other greenhouse gasses that we're putting into the atmosphere. So really, until we reverse that trend - which we're not showing much sign of at the moment - but until we do, we've got to increasingly prepare for these sorts of events."

FULL COVERAGE: All the latest on the bushfires

BUSHFIRE INFORMATION

• Advice on how to Prepare, Act, Survive
• Link to current fires and incidents in NSW, @NSWRFS

A map of fire prone areas in NSW

A statewide total fire ban has been declared for Wednesday 9 January 2013 due to the large number of fires across NSW.

• Advice on how to plan and prepare
• Link to Latest warnings and incidents in Victoria, @CFA_Updates

Danger areas in Victoria

• For information on friends or relatives affected by the Tasmanian bushfires call 1800 727 077
• Current incidents by Tasmanian Fire Service - www.fire.tas.gov.au - @TasFireService
• Tasmanian weather forecast - weather.yahoo.com

A total fire ban is in effect for all parts of Tasmania

• Red Cross Tasmanian Bushfires appeal - www.redcross.org.au, 1800 811 700, or send a cheque or money order with a note that it is for the Tasmanian Bushfires Appeal 2013 to: Australian Red Cross Supporter Service, GPO Box 2957, Melbourne VIC 8060
• Facebook page Tassie fires - we can help
• Federal Government help - The Federal Government has sent a mobile services centre to Tasmania to deliver emergency funding to bushfire victims. Emergency Services Minister Nicola Roxon said those affected could apply for emergency funding of up to $1000 per adult, and $400 per child.
• For more information about the Australian Government Disaster Recovery Payment, go to humanservices.gov.au/disaster or call the Australian Government Information Line on 180 22 66 from 8am to 8pm (local time), seven days.

• Advice to be bushfire ready - have you got a plan?
• Link to current incidents in South Australia, @CFSAlerts

• Advice on your Bushfire survival plan
• Link to current bushfire incidents in Queensland, @QldFire

• Advice on how to prepare for a bushfire
• Link to alerts and warnings in WA, @dfes_wa

• Advice on NT Fire and Rescue, @ntpolice

• Advice on fire incidents map, @ACTRFS