Ipswich and Brisbane's western suburbs are set to bear the brunt of the heatwave, with a top temperature of 39 degrees forecast at the Amberley weather station.

Should it reach the forecast temperature, it would pip Ipswich's March record of 38.9 degrees, which has stood since March 11, 2007, bureau meteorologist Janine Yuasa said.

Brisbane city is tipped to reach a high of 36 degrees on Thursday, or about eight degrees above its March average, but will fall probably short of its March record of 38.8 degrees, which has stood since 1965.

The Gold Coast is also expecting a top temperature of 35 degrees.

The extreme heat is being fuelled by a warm, dry air mass heading east from the Queensland outback, where some major centres have recorded a string of days above 40 degrees.

Birdsville, in the state's south-west, has sweltered through more than three weeks of temperatures above the marker.

Its expected top of 43 degrees on Wednesday will be its 23rd consecutive day above 40 degrees, before it drops to an predicted top of 39 degrees on Thursday.

In outback Longreach, temperatures are expected to climb above 40 for the next three days, taking its string of days above the mark to more than 10, before dropping to 39 degrees on Saturday.

Ms Yuasa said the heatwave in the state's south-east will be much shorted lived.

Thursday's extreme heat is expected to break with a cool change in the late afternoon or early evening with a cool change that could potentially bring a storm.

"The cool change will bring the temperature back down to about 30 degrees and there's just a chance of showers," she said.

"There may be a rumble tomorrow with the change coming up, possibly a couple of showers on Friday and a slight chance over the weekend."

She said temperatures in Brisbane at the weekend are expected to drop to closer to the March average of 28 degrees.