Mildura's 39.3 degrees notched Victoria's hottest day for April - 10 days into the month - while Ivanhoe in western NSW reached 39 degrees.

The warmth will shift eastwards, possibly challenging records again on Wednesday, Dr Trewin said.

For Sydney, Wednesday's forecast top of 28 degrees will be followed by three days of 30-31 degrees from Thursday to Saturday, before the mercury eases back to 25 degrees for Sunday.

By the midpoint of the month, Sydney could be running about 6 degrees above the April average of 22.5 degrees for maximum temperatures.

NSW as a whole could be about 4.5 degrees above the April norm by the middle of the month for daytime temperatures, Dr Trewin said.

The current warmth may be more notable for its duration and breadth than its intensity.

Australia set a record for April on an area-average basis on Sunday - only to have it broken again on Monday, Dr Trewin said. Cooling in Western Australia made it unlikely Tuesday and Wednesday will beat the new highs.

Other noteworthy readings include Adelaide's 36.5 degrees on Tuesday followed 36.6 degrees on Monday, the city's first consecutive days above 35 degrees, and the latest in the season for such warmth. Wednesday's forecast top of 36 degrees could make it an unprecedented trio of such days.

Another record to be smashed Dubbo's 10 days in a row above 30 degrees to start the month in April, beating the previous longest stretch in the month is six such days.

On current forecasts, the town in central NSW could notch 13 consecutive days of 30-plus weather before the heat dissipates.

While inland regions may get some much needed rain by the weekend, Sydney's dry spell will only be interrupted by light rain at times on Saturday. Other days over the coming week will be mostly dry and sunny, the bureau said.