Soaring temperatures across Tasman

Temperatures across Victoria and South Australia have surged in to mid-40s this afternoon prompting a "catastrophic" fire warning to be issued.

In the south east centre of Keith temperatures hit 44.6 degrees at 3:30pm local time with 44 recorded in Murray.

Melbourne has 43 degrees this hour with up to 44 degrees in rural parts of Victoria.

WeatherWatch.co.nz says the hot weather is being caused by the same high pressure system currently bringing cooler weather to New Zealand.

Head weather analyst Philip Duncan says it's a very typical set up when an anticyclone is in this position. "We have a large high in the Tasman Sea which is feeding hot desert air down over Adelaide and Melbourne while we're on the opposite side of the high with colder sou'west winds being dredged up from the Southern Ocean".

Mr Duncan says the same high isn't likely to bring big heat to New Zealand.

WeatherWatch.co.nz says it's relatively "cool" in Sydney and Brisbane this hour with "just 27 and 28 degrees respectively".