Autumn heat sends records tumbling

Queensland and the Northern Territory have endured their hottest March days on record in what's been an exceptional start to autumn.

A hot spell that extended across large parts of northern and central Australia earlier this month sent records tumbling, according to the Bureau of Meteorology.

In a special climate statement released on Tuesday, the BOM said maximum temperatures averaged 5-7C above average over most of the Gulf Country from March 6 to 19.

Last Thursday was the hottest March day on record for the NT and Queensland, in area-averaged terms.

Birdsville, a small town on the edge of the Simpson Desert, registered the highest temperature ever recorded in Australia for the second half of March that day - reaching a sizzling 46.5C.

South Australia and NSW also broke state records for the highest temperature so far into autumn.

A total of 30 locations with 40 years or more of data had their hottest March day on record between March 6 and 20.

Climatologist Blair Trewin said this time of year was unusual for extreme heat in the northern tropics.

"Things start to cool off as you get into autumn, so it's a lot harder to get a really high temperature in the second half of March than it is in the first half," he told AAP.

Despite the arrival of tropical cyclones Marcia and Nathan which delivered only localised falls, Mr Trewin said there hadn't been much rain in north-west Queensland or the NT since early February.

"What will typically happen is you'll have an active phase of the monsoon where it's very wet for perhaps a week or two and then a less active phase of three or four weeks," he said.

"But this year, that non-active phase has persisted for longer than usual.

"So it's been persistently dry through that northern region, and with clearer skies and also drier ground conditions than is usual for this time of year, that's an ideal environment for persistent extreme heat."

The hot spell is likely to have exacerbated the impact of the drought in western Queensland - a situation that could worsen if El Nino develops later this year.

"Were that to happen, that would shift the odds towards hotter and drier conditions over a lot of, particularly eastern, Australia for the second half of the year," Mr Trewin said.

MARCH MADNESS

* 39.99C - hottest March day on record for the NT, in area-averaged terms (March 19), beating the previous mark of 39.87C (March 3, 1988)

* 38.73C - hottest March day on record for Queensland, in area-averaged terms (March 19), beating the previous mark of 38.41C (March 1, 1923)

* 46.5C - highest temperature ever recorded in Australia for the second half of March, at Birdsville, Qld (March 19)

* 44.0C - highest maximum temperature for March in the NT, at Jervois on March 19 (previously 43.9C at Finke, March 16, 1968)

* 45.4C - highest temperature in South Australia so far into autumn, at Moomba on March 19 (previously 45C at Maree, March 11, 1973)

* 42.9C - highest temperature in NSW so far into autumn, at Mungindi on March 19