winter with the average maximum temperature up nearly two degrees Celsius (C) above the long-term trend, according to ABC News.
The 2017 winter was the hottest since 1910 when national records began, according to Bureau of Meteorology figures released recently.
The average maximum daily temperature recorded across all Australian recording locations for June, July and August 2017 was 23.7 degrees C.
The warm weather was most pronounced in the north of Australia.
It was the hottest winter on record for Western Australia, Queensland and the Northern Territory (NT), while New South Wales and South Australia made the top three.
Daily minimums were also warmer than average in most of northern Australia but not as far above average as the maximums. In contrast, inland NSW and northern Victoria had notably cold nights with many areas one degrees C to two degrees C below average.
NSW had its coldest average winter nights since 1997.
Meanwhile nationally it was the ninth driest winter on record. The only large area to record rainfalls significantly above average was a pocket of central NT as a result of one rain event in mid-July.
Andrew Watkins, manager of extended and long-range forecasts at the Bureau of Meteorology, said the real reason for the warmth was the persistent high pressure seen particularly during early winter.
“But you also have to add to that the long-term warming trend,” he said.
Evaporative cooling is the same process that cools you down when you sweat, taking energy from the surrounding air to convert liquid water into gaseous water vapour, leaving the surroundings cooler.
Without a lot of water on the ground this year, large scale evaporative cooling could not happen.
The clear skies also explain the low minimum or overnight temperatures in the southern states.
Without a blanket of clouds, the heat from the day is lost to space, and temperatures drop overnight.
But that is not all, Dr Watkins said: “We’ve also seen fewer cold fronts able to penetrate inland due to the slow moving and more southerly highs acting as a barrier to their normal northward progression”.
So not only has high-pressure prevented rain in the north but it has also prevented
the cold fronts which normally bring rain in the south during winter.
According to the climate scientists at the Bureau of Meteorology, the story behind the heat in northern Australia is more about what has not been happening.
In a standard winter there would be several south-easterly surges, bringing cold air into the tropics.
This year these surges were almost completely missing — blocked by that high pressure — until very late in the season.