Australia has seen its hottest July in the hundred years since records began.

The national mean maximum temperature for July was 2.62℃ above the average maximum temperature and 0.66℃ above the previous record in 1975.

BOM senior climatologist Blair Trewin says warm weather caused by high pressure ridges over the sub tropics is for July, but they are usually met by big lows hitting the south.

This year, those deep southerly flows have not arrived to push cool air up into central and northern Australia.

“That’s something that just hasn’t happened this year,” he said.

The northern part of Australia felt most of the heat, with average maximum temperatures in much of Queensland, the Northern Territory and Western Australia hitting their highest point on record.

New records were not set in Australia’s south, but the average maximum was still 1℃ above the average.

Inland NSW and northern South Australia saw significant warmth, with temperatures up to 3℃ above the average maximum, and a warm front in late July bringing record maximum daily high temperatures in NSW, Victoria, WA and SA.

“The long-term warming trend changes the risk, the sort of weather extremes you might have got once in a hundred years at the start of the last century, you may now get once in 20 years or once in 10 years now,” Mr Trewin said.