After passing 40 degrees in Sydney yesterday, temperatures dropped to the mid-twenties today, although hotter weather is forecast to return by the weekend, and officials are warning against any complacency.

More than 2000 firefighters are on duty with up to 30 fires still out of control across New South Wales.

Michelle Taverniti is a reporter with 2UE news in Sydney - she says many of the blazes are thought to have started accidentally, but police investigations are underway into the causes of others:

Australia's record heatwave is now so intense that meteorologists have had to invent new colours for their maps to accommodate predicted highs of FIFTY degrees Celsius.

Four areas of the state were earlier issued with "catastrophic" fire warnings. The Rural Fire Service there say strong winds are fuelling the flames.