Brisbane has started to cool down after lingering moisture meant the maximum temperature was slightly shy of the 39 degrees forecast.
The mercury peaked in Brisbane city at 3.23pm, with 37.9 degrees recorded in the city.
The temperature will continue to spiral, with a minimum of 21 degrees forecast for Brisbane city overnight.
Shortly before 4pm, Bureau of Meteorology forecaster Andrew Bufalino said the dry air was still on its way, but moisture was being sucked from the air.
The temperature just after 3pm was 37.5 degrees.
“It’s a bit of a rollercoaster at the moment, waiting for the dry air to reach the region,” he said.
“The moisture is dropping away rapidly at the moment. We will get pretty close.”
Electricity demand has continued to grow as the mercury climbs; at 3.30pm, Energex lists usage as extreme on their website, with 4310 megawatts being drawn, down from 4520 megawatts earlier in the day.
It was a record for the year, but still short of the February 2010 record peak of 4670 megawatts.
Energex reports 441 customers are without power across southeast Queensland and the energy provider is asking customers to think about their electricity usage.
Fire warnings ranging from severe to extreme are still in operation, however the Rural Fire Service reports there are no current fire bans in the state.
It should remain quite hot even into the evening hours
There are about 30 bushfires burning across the state, however none are considered a major threat to property.
Just after midday, electricity demand reached 4061 megawatts, a record for the year, but well short of the 4636 megawatt record set in February in 2010. Shortly before 1pm, the demand had reached 4133 megawatts.
Just before midday, the temperature had hit 34.5 degrees; however wind and humidity brought the temperature up to 36.6 degrees.
The Queensland fire service has recorded 32 bush fires across the state, however none are believed to be posing any major threat to property.
A spokeswoman for the Queensland Ambulance Service was unable to provide figures on heat related illnesses for this morning, however in the days leading up to the heat wave, four people had been taken to hospital suffering from heat stroke and other illnesses caused by the high temperatures.
Temperatures of up to 41 degrees are expected across the state on Tuesday, with Stanthorpe, Toowoomba, Dalby, Ipswich, Kilcoy, Boonah and Beaudesert among the worst affected.
Fire warnings ranging from severe to extreme have been issued by the Bureau of Metrology, with the possibility of strong winds across some sections of the state.
The temperature in Brisbane is not expected to peak until 3pm when the bureau predicts the mercury will hit 39 degrees, the hottest temperature in Brisbane since 2011.
By 8am, the temperature had already exceeded 27 degrees and at 10am the Bureau of Meteorology recorded 33 degrees in Brisbane. By noon the mercury had reached 34.6 degrees in Brisbane, but Brisbane Airport was slightly cooler with a reading of 28.7 degrees.
Other temperature readings around the region at noon included 34 degrees at Archerfield, 37.5 at Beerburrum, 36.1 at Gympie and 36.9 at Nambour.
The heat has two-thirds of Queensland on bushfire watch, as temperatures in parts of the state soar to more than 40 degrees for the fourth consecutive day.
In Brisbane the temperature is forecast to climb rapidly throughout the morning, reaching 34 degrees by midday.
But the temperature will not peak until mid-afternoon, when it is set to hit 39 degrees – 10 degrees above the December average – about 3pm.
"It's going to be very, very hot," Bureau of Meteorology forecaster Michelle Berry said.
"It should remain quite hot even into the evening hours."
A trough extending over the state's north-west to the south-east corner around the Darling Downs is generating the hot conditions.
The dry westerly winds fuelling the hot conditions, however, will provide some relief from the humidity.
The temperature will not remain at 39 degrees for much longer than 30 minutes, before falling into the low-30s.
The last time Brisbane experienced a December top of 39 degrees was Boxing Day 2001.
But the hottest December day on record came on December 7, 1981, when the mercury topped 41.2 degrees.
The heat has been even more intense in the state's west of late, with temperatures in Mt Isa and Longreach forecast to hit 40 degrees on Tuesday – the fourth successive day at 40 degrees or above.
Controlled fires are presently burning at Beachmere, north of Brisbane and near Mount Isa, where a Brisbane-based fire crew was sent on Monday.
Queensland Fire and Rescue director of rural operations Peter Varley said any fire that started today would be extremely difficult to control.
"The farther west, the worse the conditions get," he said.
The Queensland Fire and Rescue Service has mustered additional resources across the state's south-east should the worst occur.
A strike team from Toowoomba arrived in Roma on Sunday and incident control points have been established in Warwick, Dalby and Roma.
Six water bombers and two aerial support aircrafts are also positioned across various parts of south western Queensland.
An enhanced fire danger for Brisbane is expected to continue on Wednesday, even as temperatures drop back to 32 degrees.
Queensland Health has urged residents to drink plenty of fluids and remain in air-conditioning where possible to avoid suffering heat stroke or exhaustion.
‘‘The effects of overheating on the body can vary from heat rash and cramps through to heat exhaustion or heat stroke,’’ Queensland Health said.
Residents are also asked to check on elderly neighbours, or friends and family, who may be more vulnerable in the hot weather.
Heat exhaustion usually develops over a couple of days.
Symptoms may include muscle cramps, heavy sweating, paleness, dizziness, nausea or vomiting and fainting.
People suffering heat stroke require urgent medical attention. Tips to prevent heat-related illnesses:
- Drink plenty of fluids - cool water is best. Don’t wait until you are thirsty to drink, but drink regularly throughout the day. Urine colour is a good guide to hydration - it should be clear to light straw-coloured, not dark or gold.
- Stay indoors in very hot weather, preferably in an air-conditioned building or ensure there is good air flow with fans and open windows.
- Public venues, such as air-conditioned shopping centres and pools, can provide refuge from the heat.
- People can also stay cool by taking cool showers or baths; soaking their feet in a basin of water; or wetting a bandanna or washer and wrapping it around their neck.
- Marissa Calligeros, Bridie Jabour and Amy Remeikis