Towns deserted as locals seek relief from roasting heat

In the bone dry heat of a dusty outback town, the streets are ghosted.

"All the blokes working on the council here will go home at lunchtime," southwest Queensland's Bulloo mayor John Ferguson - better known as "Tractor" - told AAP.

"Once it gets to about 44, 45C they'll go home and get under the air-conditioner or go for a swim down the river, in the big waterhole in front of the town.

"Who knows what the bitumen is? It could be 60 or 70C or even hotter. You don't want to be out shovelling dirt in that."

At Thargomindah, in Queensland's Channel Country, locals are enduring a prolonged heatwave in near record-breaking conditions.

The all-time mark of 48.8C was under threat before peaking at 48.5C as the dangerous heatwave that has cooked South Australia and Victoria creeps into Queensland and NSW.

Local temperatures may fall short of Queensland's record high of 49.5C recorded in Birdsville back in 1972, but it's still not pleasant.

"There's not a soul in the street," resident Donna Humphris told AAP.

She said locals all had a go-to place to keep cool in the event of the power grid going down under the strain.

Thargo, as it's known to locals, has already been through a lot.

In April last year the town was smashed by flooding, with the Bulloo River peaking more than a metre above the previous record.

Ms Humphris - still living in a caravan after the event - says many residents lost their backup power generators.

As a last resort Ms Humphris may sleep on a mattress she has kept in the back of the small supermarket she owns.

Sleeping is tough for everyone.

"At midnight the other night it was still 39C," Mr Ferguson said.

A lack of airflow has meant the heat has "just sat there" in southwest Queensland, the Bureau of Meteorology said.

"With no significant cold fronts across southeast Australia to flush it out, it's allowed the heat just to remain there and has led to really prolonged, severe heatwave conditions," senior forecaster Felim Hanniffy said.

Relief for inland NSW and Queensland residents may not come until the weekend when a cool change is expected.

That would push the heat briefly back into Queensland's southeast, with the possibility of thunderstorms.

In NSW, temperatures in Ivanhoe in the state's west was forecast to reach a maximum of 48C and opal mining town White Cliffs may hit 48.9C.

In Victoria's record breaking heatwave, northern areas are on track to record eight straight days with maximum 40C temperatures with about 11,000 properties still without electricity.

The state's north was enduring its fifth straight day on Wednesday, with relief not in sight until Sunday when the mass of cooler air arrives.

Victoria smashed its own heat record as Walpeup in the state's north hit 48.9C on Tuesday.

"It is really important to stay hydrated to avoid excessive heat exposure and to check on vulnerable members of your community," Federal Emergency Management Minister Kristy McBain warned on Wednesday.

"Heatwave conditions, combined with dry and dusty winds, continue to create a significant risk in multiple states."

Coastal cities were enjoying a brief reprieve, with Melburnians experiencing a top of 24C on Wednesday and a high of 33C in Adelaide.

Just 24 hours earlier, Melbourne recorded a top of 42C, a few degrees short of its record high.