This year has already seen very warm conditions in NSW and a warm July - about 1 degrees above the long-term norm.
Statewide July itself will come in as the third-warmest in NSW since records began.
It will require ''quite a dramatic change'' for 2013 not to be among the hottest years on record for Australia, said Blair Trewin from the national Climate Centre.
Year to date, average mean temperatures are running 1.07 degrees above the 1961-90 baseline, placing the year just behind 2005, the hottest in more than a century of national data.
The exceptional warmth began last September and every month has turned in notable weather.
Blair Trewin says one factor influencing conditions has been unusually warm sea-surface temperatures right around the country.
To the end of June, ocean temperatures are wavering about half a degree above the long-term average, meaning onshore winds are warmer in virtually any direction they blow. In a century of records, Australia hasn't recorded a below-average temperature for 20 years, he says.
The result will be that temperatures for the rest of the year should remain above average.
The three-month outlook is also for above-average temperatures and in NSW above average rainfall is very likely with an 80 per cent chance of higher than average rainfall.
© ABC 2013
16:28 EDT Hail is caused when raindrops are lifted up into the atmosphere during a thunderstorm and then supercooled by temperatures below freezing, turning them into ice balls.