Australia is set to experience more heatwaves, with record-breaking hot weather becoming "normal" across the continent as climate change pushes up land and sea temperatures, a government report warned Thursday.



The biannual State of the Climate report from the Bureau of Meteorology (BOM) and national science body CSIRO said Australia was already experiencing more extremely hot days and severe fire seasons, and projections showed temperatures would likely keep rising.



"Australian temperatures will almost certainly continue to increase over the coming decades. Temperature projections suggest more extremely hot days and fewer extremely cool days," CSIRO senior scientist Helen Cleugh said.



"As land temperatures increase, so do ocean temperatures and the report shows that the deep ocean is also impacted, with warming now recorded at least 2,000 metres (1.24 miles) below the sea surface."



The country experienced its three warmest springs on record between 2013-15, the weather bureau said. Spring, between September to November, is the period when temperature and rainfall are critical to southern Australia's bushfire season.



While there has been more rain in some areas, there has also been a "significant seasonal decline" in others, including an 11 percent drop during the April-October growing season in Australia's southeastern region since the mid-1990s, BOM added.



"The changing climate significantly affects all Australians through increased heatwaves, more significant wet weather events and more severe fire weather conditions," said the bureau's climate monitoring manager Karl Braganza.



"Some of the record-breaking extreme heat we have been seeing recently will be considered normal in 30 years' time."



Cleugh said changes in the climate was due to an increase in greenhouse gases such as carbon dioxide, which were keeping heat in Earth's lower atmosphere.



She added that this year CO2 levels would reach a global annual average of over 400ppm (parts per million) -- the highest in two million years.



Australia has warmed by approximately 1.0 degree Celsius (1.8 Fahrenheit) since 1910, with the number of days each year that post temperatures of more than 35C increasing in recent decades except in northern Australia, the report said.



Meanwhile, rainfall has reduced by 19 percent between May to July in southwestern Australia since 1970.



While bushfires are common in Australia's arid summer, which usually begins in December, firefighters have said they are observing deteriorating conditions, including an apparent increase in the number of the most severe blazes in recent times.