A heatwave warning has been issued for parts of Queensland with some areas of the state's west surpassing 40 degrees Celsius.
The Bureau of Meteorology (BOM) said severe conditions were expected in the north-west, northern to central interior and south-east inland, increasing to extreme from tomorrow in parts of the north-west.
Temperatures today reached 43.6C in Birdsville, 42.2C in Longreach and 41C in Trepell shortly after 1pm.
About the same time Brisbane was 35.4C, Amberley reached 36.8C and Gatton 37.4C.
The Sunshine State has experienced a very mild start to summer, with a low hovering off the Queensland coast last week producing cool, wet weather.
But BOM senior forecaster Steven Hadley said the departure of that low meant warm air which had been building up over the north of the country was now tracking south into Queensland, bringing scorching temperatures.
"That could potentially mean that we see some severe intensity heatwave conditions," he said.
"Over the next few days, temperatures could be 10 or 15 degrees [Celsius] above what they were on the first of December."
At this stage no records are likely to be broken, but temperatures are set to be 40C as far east as St George on Wednesday and Emerald on Thursday.
Mr Hadley said it would be even hotter in outback Queensland mid-week.
"We're expecting the top temperature in the state this week to be somewhere around Birdsville, getting potentially around 45C or 46C on Wednesday," he said.
He said the heat might also generate some isolated severe thunderstorm activity on Wednesday and Thursday over the south-east.
"Because of the really high temperatures and fairly dry air mass, we could see some fairly gusty winds coming out of those thunderstorms on Wednesday, but possibly not too much rainfall," he said.
Mr Hadley said there might be some showers on Thursday, with temperatures beginning to drop that night.
"I think it's really going to be Friday when we start to see the majority of places in the south-east seeing some appreciably cooler weather, with temperatures getting back down mostly into the mid to high 20s, although we could still see a few 30s around inland in the south-east, even on Friday."
Plea to ensure vulnerable people are kept safe
Queensland Ambulance Service said elderly people, young children and people who work outdoors can be especially vulnerable in hot temperatures.
Clinical director Tony Hucker urged Queenslanders to check on elderly neighbours.
"Make sure they've got plenty of cool water, they've got food that they can have regular smaller meals and also make sure their house is well ventilated, if they've got air-conditioning that it's on, if they've got fans, they are on," he said.
"Mums with young bubs make sure they're having regular feeds, the normal amount of wet nappies and just keep an extra special eye on them."
It is important to know when to seek medical assistance, Mr Hucker said.
"If people can't drink, they can't keep it down or they're vomiting, that's when you need to call triple-0," he said.
"If people have got minor illnesses from the heat it's perfectly reasonable to call 13 Health."
