Buried in the Bureau of Meteorology's monthly report on national conditions, the agency noted the 12-month mean temperature was a "solid highest-on-record" result.

In fact, mean temperatures were a full 1.08 degrees above the long-term average, smashing the previous record July-June anomaly by 0.18 degrees. The previous record was set in the 12 months to June 2010 – an El Nino period.

“The July-June year anomaly can be interesting as it provides a way of examining conditions across the warm season as a whole, which can capture the influence of signals such as El Niño and La Niña,” the bureau said.

That influence may continue, with the bureau also reporting that fresh signs of an El Nino have been identified in the Pacific during the past fortnight. During El Nino years, much of Australia tends to cop warmer and drier than usual weather, making active bushfire seasons and droughts more likely.

“We’ve still got the set-up for an El Nino,” said Andrew Watkins, manager of climate prediction services at the bureau, noting the likelihood of such an event remains "at least a 70 per cent" chance.

Ocean conditions have been primed for an El Nino for some months with waters in the central and eastern Pacific unusually warm. Meteorologists have been watching for evidence the atmosphere would “couple” or respond, signs of which have lately appeared.

These include a weakening of the easterly trade winds and increased cloud formation in the region where the dateline and equator intersect. The Southern Oscillation Index (SOI), a key gauge, had also dropped sharply.

“If the winds and the cloud and the SOI continue with the current trends, they may well reach true El Nino levels, and hence start to feed back on the ocean,” said Dr Watkins.

Conditions are similar to 2009 - the previous El Nino year - with current observations and models pointing to an event developing by spring.

Warm start to 2014

Australia posted its hottest year on record in 2013 and this year has also got off to a warm start.

NSW, Queensland and Victoria all posted record mean temperatures for the first half of 2014, with June also much warmer than normal, the Bureau of Meteorology said. Australia-wide, it was the fourth-highest start to a year.

In June alone, nationwide rainfall was 32 per cent below average for the month. Over the past year, areas such as north-east NSW and south-eastern Queensland have reported rain very much below average while northern regions and Tasmania have had relatively good rains.

Over the past 12 months, mean temperatures were also the highest on record for the states of NSW, Queensland and South Australia.

For south-eastern Australia, the late arrival of winter saw more temperature records tumble in June.

The near-term outlook has Melbourne expecting days with maximums of 15-16 degrees over the next week, or about 1.5-2.5 degrees above average for July.

In Sydney, the next week should also be warmer than average by about the same margin, with daily tops expected in the 18-20 degree range.

Australia’s mean temperatures have risen about 0.9 degrees over the past century as the global climate has warmed. Comparing the past 15 years with the 1951-1980 period, the chance of a very warm month has increased five-fold and the frequency of very cool months had dropped by about a third, the CSIRO and the Bureau of Meteorology noted in their latest State of the Climate report released earlier this year.