The Bureau of Meteorology has just upped the chance of an El Nino this year, meaning there is now three times the normal risk of the climate driver associated with hot and dry conditions happening this year.
Senior climatologist Robyn Duell said it had been a slow boil.
"We've been hovering at an El Nino watch for a long time going 'Will it? Won't it?'" she said.
But Ms Duell said in the past three weeks staff had seen a little bit of a kick in the eastern Pacific Ocean temperatures, which was finally showing up in the winds.
"We've seen a response in the atmosphere. That's why we've raised our alert up from a watch to an alert," she said.
An El Nino is the phase of the El Nino Southern Oscillation (ENSO) where the trade winds over the Pacific are weakened and even reversed, reducing the moisture avaliable on the east coast of Australia.
"Any given year there is a risk because El Nino is a normal part of our climate system. We get an El Nino on average every two to five years," Ms Duell said.
"That puts the risk at any given year at about a 25 per cent chance. At the moment we're looking at around a 70 per cent chance.
"This is absolutely not the type of outlook I think that many people would be hoping to hear."
Potential for dry start to northern wet season
Widespread drought has been biting this year, especially in New South Wales.
"The dry conditions are very severe in large parts of eastern Australia and it's been quite devastating, the impacts for a lot of people," Ms Duell said.
She said an El Nino at this time of year would typically lead to a poor end to the southern wet season as well as a dry start to the northern wet season.
"Unfortunately the outlook does suggest for many that it's likely to be a dry end to the year."
Ms Duell said it had also been an unusually warm year — the warmest January to September on record for NSW and the Murray-Darling Basin.
The hot conditions intensify droughts as well as working together to increase the risks of heatwaves and bushfires.
But El Nino does not have a complete sweep on the disaster stakes — there is a relationship between El Nino and reduced numbers of cyclones, but people should not be complacent.
"Despite there being a reduced chance of tropical cyclone activity, this baseline risk that we always have every year still remains to communities in the north," Ms Duell said.
There has been at least one cyclone in Australian waters every year since records began, and it only takes one to be devastating.
El Nino not acting alone
Ms Duell said there was cool water to the north-east of Australia that indicated the country could currently be in the positive phase of the Indian Ocean Dipole (IOD) climate driver.
The IOD drives circulations across the Indian Ocean in much the same way as the ENSO does over the Pacific.
The positive IOD is the phase associated with dry conditions in Australia.
Ms Duell said El Nino and positive IOD events often worked together, occurring at the same time and often reinforcing each other.
"A positive IOD has likely been contributing to the drought conditions we've already seen across parts of the country," she said.
The two climate drivers teaming up could add to the woes.
"When we see El Nino and IOD potentially occurring together … we often see more widespread rainfall deficits occur."ABC