The Bureau of Meteorology has confirmed that Australia has just experienced its hottest summer on record.

The bureau says the previous hottest summer - measured by average day and night figures from across the nation - was in 1997-98.

Climate monitoring manager Dr Karl Braganza says a particularly hot spell in January has helped towards the new record.

"That's certainly contributed to it being the hottest summer on record, but it has been hot in December and February as well," he said.

"Both of those months right around Australia have been warmer than average and it's extending a real six-month period, so the last six months have been the hottest on record from September to February."

Overall, Australia's average summer temperature came in at 28.6 degrees Celsius.

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Fourteen of the weather bureau's 112 long-term climate stations recorded their hottest days on record, including one in Sydney, where the temperature hit 46 degrees in the middle of January.

"Certainly there's a background trend of warming temperatures and there's also a trend in our rate of setting records particularly in the last decade," Dr Braganza said.

"Now we're setting daytime and night-time records around Australia at a very (much) more frequent rate than we were in the past and they outnumber cold records by five to one in some instances."

And he says this summer is likely to be a taste of what is to come in future decades.

"By about mid-century, so in about 40 years, you're actually talking about conditions like this becoming normal," he said.

"It depends on what emissions trajectory we go down, but on those mid to high scenarios, then this certainly would be a taste of things to come."

Extreme heatwave

Blair Trewin, a climatologist at the bureau, says the hot weather was experienced across almost all parts of the country.

"Most hot summers it's very hot in the east and cool in the west, or it's hot in the south but cooler than normal in the north, but this year it's been hotter than normal almost everywhere," he said.

"We had an extreme heatwave through the first half of January which affected much of the country and that was the peak of the summer heat.

"But even if you take out that first half of January, it was still a summer which was very much warmer than normal."

The flood disasters may give the impression that it has been not only a hot, but a wet summer, but the bureau says average national summer rainfall was at a nine-year low.

"If you look at the areas that have had above average rainfall, you are really only looking at two areas," Dr Trewin said.

"One is the east coast and adjacent ranges, from probably about Mackay southwards in Queensland and most of coastal New South Wales, and also the western half of WA. So those two regions had a wet summer but almost everywhere else it was a dry summer."

No El Nino

Normally, a hot summer like the one just gone would be accompanied by hotter than normal temperatures in the central and eastern Pacific Ocean - an El Nino summer, in other words.

But Dr Trewin says this year ocean temperatures were average.

"That's quite unusual for a summer like this," he said.

"If we look at previous very hot summers in Australia before this year, six of the eight hottest summers on record had occurred during El Nino years.

"So the fact that we've got such a hot summer without having an El Nino makes it in some ways even more exceptional."

Penny Whetton, a senior climate research scientist with the CSIRO, says the fact that it was not an El Nino year is significant.

"It just underlines that it's much easier, so to speak, for the climate to give us a hot year than what it used to be in the past," she said.

"It really just shows that the potential for us to get really warm conditions has increased.

"The effect of that is that we can get very warm years now without one of the factors that can contribute to warmth being in place, and that is El Nino conditions. I think that is actually quite significant. "