A severe to extreme heatwave is on its way for many parts of Queensland this weekend, and the Bureau of Meteorology (BOM) is warning residents to prepare.

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Temperatures will start to build from Friday, soaring above 40 degrees Celsius in some western, central and northern parts of the state on Sunday and to between 35C and 40C along the eastern coast.

The heat will linger for most of the week and records could tumble as some areas experience extreme heatwave conditions, forecaster Sam Campbell said.

"So really hot overnight temperatures up to 8C above average," he said.

"For many people they won't see overnight temperatures dropping below 30C overnight and then the daytime temperatures getting up into the 40s and approaching, say, 45C around Longreach."

"So it is actually going to be a significant heat event for Queensland.

"It's going to come with a risk for people who are vulnerable to heat as well, so it's a pretty serious message there for elderly people, you know people who are unwell and people who are more exposed to the heat ... and don't have air-conditioning."

Mr Campbell said a hot air mass would start to build in the south-west of the state from Friday, spreading further east and north over the coming days.

'No relief in sight'

The BOM predicted temperatures in the major south-eastern metropolitan areas would reach around 35C, with a top of 36C around Toowoomba, 43C around Longreach and 45C at Birdsville.

Rockhampton could reach a maximum of about 35C, while areas around Mount Isa in the north-west were expected to hit the low 40s, Mr Campbell said.

"In fact there's no real relief in sight," he said.

"It's a combination of an upper-level system that's producing a really hot air mass, and then not seeing any air mass changes. No weather systems coming through that bring in a cool air mass from the south or from the west.

"So the hot air just sits there building up, getting hotter and hotter each day, and that's why we're going to see these hot conditions persisting for quite some time."

Mr Campbell said residents in affected areas should pay attention to advice from the Queensland Ambulance service and Queensland Health.

The Queensland Ambulance Service (QAS) is warning people could be struck down with a heat-related illness if they do not take necessary precautions in high temperatures.

A spokesperson said warning signs included headaches, nausea, cramps, fainting, excessive sweating, tiredness and dizziness.

Residents should stay hydrated, wear cool clothing, stay out of the sun and watch out for vulnerable friends and neighbours.