“The risk of an El Nino is significantly elevated from the long-term average,” Dr Trewin said.
Autumn was dry across southeastern and southwestern Australia, with Melbourne and Perth coming within millimetres of setting a record low for rainfall between January and May.
Melbourne, for the first five months of the year, had the third-lowest rainfall on record with just 101mm. The lowest was 1967 with 98mm for the five-month period, followed by 1923 with 99mmm.
Perth also missed setting a five-month record low by a couple of millimetres.
All the six states and the Northern Territory had below normal rainfalls for autumn.
“For the Murray-Darling Basin, we have now had below-normal rainfall in each of the last nine autumns, and 17 out of the last 19,” Dr Trewin said.
In Victoria, only three of the past 19 autumns have had above-average rainfall, “and the last nine have all been below normal”, he said.
Most of inland eastern Australia had rainfall that was between 40 and 60 per cent below normal this autumn, while most of the western half of Western Australia was at least 40 per cent below normal.
“Over quite a bit of the west coast (there was) anything from 60 to 90per cent below normal,” Dr Trewin said.
But there were exceptions: the east coast between the Hunter Valley and Fraser Island had well above average rainfall; and there was above average rainfall in southwest Tasmania, parts of the Nullarbor and parts of inland Western Australia.
Southeast Queensland had an autumn rainfall that was well above average, with several daily and monthly records set for May, particularly in the Sunshine Coast and Brisbane areas, where flooding occurred.
The wettest site in Queensland was Bellenden Ker Top Station, in the northeast of the state, which received 2348mm for autumn. The wettest single autumn day occurred at Godwin Beach on May 20, when 332mm fell.
In central Australia, the past week has been wet and cold, with substantial rain over the weekend. Yulara, near Uluru, had 17mm for May, and a maximum of 13C over the weekend, while Alice Springs got 21mm across the weekend and endured a record low for May of just 9.6C on Saturday.
Across Australia, Dr Trewin said daytime maximum temperatures were above normal for autumn and overnight temperature right on normal.
“Daytime maximum temperatures averaged over Australia were 0.53C above normal and minimum temperatures 0.2C below normal – so warm days but near-normal nights,” he said.