Adelaide has recorded its hottest ever run of December days, with the mercury hitting 40 degrees Celsius on Saturday.
The Bureau of Meteorology (BoM) confirmed that Adelaide was sweltering through its fourth consecutive day over 40C, making it the city's longest December heatwave since records began.
"We have a high pressure system over the Tasman Sea that's not really moving anywhere, we've got anti-clockwise winds around that high pressure system and very hot and dry northerly winds bringing very hot air from inland Australia's towards Adelaide," Anolak told The Huffington Post Australia.
It is the second outbreak of extreme weather in Adelaide this month and December 7 was Adelaide's hottest December night ever, with a minimum of 30.3C.
Strong, hot winds will make for a scorcher down south.
Blenheim is expected to reach a record-breaking 35 degrees Celsius.
Christchurch is also heading for one of its hottest December days on record with temperatures tipped to reach 33C.
But the howling 100kmh Northwest wind may sabotage any outdoor plans.
The hottest temperature recorded in Christchurch for December was 35.4C in 1975, followed by 33.5C in 1994, according to MetService. Christchurch's hottest ever day was 40C in February 1973,
For Monday, MetService has forecast a high of 33C at Christchurch Airport, which could rank as the second or third hottest December day for the city.
MetService meteorologist Tom Adams said the conditions were due to a warm air mass moving from northern Australia.