Southern Australia is gearing up for another day of extreme temperatures and high fire danger at the end of a heatwave which has set records across large parts of the country.

By mid-morning, temperatures in Adelaide had hit 38 degrees on the way to 42 degrees, while Melbourne was above 36 degrees on its way to 44 degrees. Further north, the mercury had risen to 30 degrees in Canberra on its way to 41.

Relief will come quickly to Melbourne tonight, with the cool change expected to hit about 8pm and dropping up to 15 degrees in an hour.

Until then though, Bureau of Meteorology forecaster Stewart Coombs said temperatures would remain high. 

“Once the change comes through it will fall quickly, at least 12-15 degrees in the first hour so it will be a very dramatic change in terms of temperature and wind; it will be an extremely squally change.”

Mr Coombs warned there would also be a chance of thunderstorms following the change, as well as strong wind conditions.

The cool change is likely to play havoc with fires in South Australia as well, with the change followed by thunderstorms and strong southerly winds.

summer in Adelaide, going for 42c again…107f…going to beach…..then aircon & more movies! & beers! pic.twitter.com/amH4Tj5jfQ

— Sue Louise Pierson (@SuePierson11) January 17, 2014

Adelaide Bureau of Meteorology forecaster Mika Teace said the change was likely to start in the afternoon, with the real relief to come later in the evening and overnight.

“It’s a very tricky change because .. it is coming off the cold ocean into hot air over land which is slowing it down so it is difficult to predict when it will come in.

“We’ve had a hot start to the day with a maximum of 37, but there is now cloud cover taking the edge off the heat.”

Victoria

This week’s heat in Melbourne put it on track for its record-breaking fourth straight day above 41 degrees on Friday.

“We’re looking pretty good for 44 today,” bureau spokeswoman Clare Mullen said.

“All our records in the past only managed to get three days in a row over 41. We’ve had hotter temperatures but what’s been different with this one is it’s been day after day.”

The potentially record-breaking stretch comes a day after Melbourne recorded its hottest day since Black Saturday, reaching 43.9C on Thursday.

The mercury is also tipped to rise to 44C in Horsham near the Grampians on Friday, with the chance of a late storm.

This week’s hot weather has taken a toll on Bendigo’s airport. Mayor Barry Lyons says the high temperatures had caused the runway to bubble and crack.

The Country Fire Authority’s Paul Tangey says today will be the most dangerous day of the week, and that a change is expected tonight.

“There’s predicted to be a little bit of rain over the weekend but the change will mean slightly cooler temperatures, so down to the low 30s and high 20s,” he said.

Some struggled with the extreme conditions, with Ambulance Victoria recording 13 cases of heat exhaustion and seven cardiac arrests from midnight until 6.30am (AEDT).

South Australia

In Adelaide, residents are in for their fifth straight day of extreme heat. Extreme bushfire conditions are also set to grip parts of South Australia as large swathes of country swelters in very hot and dry conditions.

If Adelaide passes 40C today, it will make it the city’s fifth day in a row of 40C-plus temperatures, making it the third worst heatwave on record. In 1908 and 2009 Adelaide sweltered through six days above 40C.

We spotted a very sweet gesture on Waymouth St in the West End this morning. http://t.co/c4HTc5uel0 #Adelaide pic.twitter.com/ojnsyx5Y9u

— Already Home (@alreadyhomeADL) January 16, 2014

BoM forecaster Brett Gage said a southerly change late on Friday afternoon would see the temperature drop, with a maximum of 28 degrees forecast for Adelaide on Saturday.

He said the temperature would probably be highest in the state’s Riverland district, with Renmark tipped to hit 45 degrees.

The temperature at Renmark Airport at 7.50am was already 26.4 C.

“Around the Riverland district looks like the highest for today,” Mr Gage confirmed.

Beating the heat with a seat at the beach. Photo: AAP

Meanwhile, the Country Fire Service (CFS) says extreme bushfire conditions are current for the state’s lower southeast and upper southeast districts.

The CFS advises that 35 fires are burning across the state, with a watch and act alert current for a blaze in the Southern Flinders Ranges.

The agency says the fire is burning near Port Germein, at Gorge Road, Bridle Track, Telowie Road, Stock Road, Pole Road and the Middle Track Road.

“The fire is not controlled and is burning in scrub, and conditions are continually changing. The CFS is attending to this fire,” it says on its website.

— with Melissa Mack, AAP