Much of Victoria will again face heatwave conditions and elevated fire risks in coming days, with temperatures in some towns in the state's north-west likely to exceed 40 degrees Celsius for at least six days in a row.
Weak cool changes will spare Melbourne some of the worst of the extremes, but the city could still expect 39C today.
Another bout of heat returns on the weekend with 36C and 39C forecast for Saturday and Sunday, according to Australia's Bureau of Meteorology.
''The pattern's set up for almost a stubborn hot air mass that's very hard to move from inland parts of NSW and Victoria,'' said Richard Russell, a duty forecaster in the bureau.
Tuesday's cool change may not reach Melbourne until after 7pm, Russell said.
Winds, particularly in the state's west, would be fresh to strong, with gusts reaching as much as 90kmh making it tough for fire crews, he said.
Mildura on the Murray reached 38.8C on Monday and could expect at least six days of 40C or wamer weather.
"For most places, the intensity of the heatwave will be slightly less, but the length of it is going to be a bit longer than the last one," said Rob Sharpe, a meteorologist at Weatherzone.
Victoria's heatwave earlier this month broke records, with Melbourne recording four consecutive days above 41C for the first time.
Health authorities estimate that as many as 139 people died in excess of the numbers normally expected, with the extreme heat a likely factor.
The bureau's new heatwave forecasting service indicated most of Victoria would experience heatwave conditions from today until at least Sunday. By Sunday, most of the state, along with south-eastern South Australia and southern New South Wales, would have severe heatwave conditions.
Melbourne was likely to get a weak cool change by late today, but the fresher winds would also raise fire-danger ratings across the western half of the state in particular.
''There's the potential for Sunday to be even warmer than (Tuesday),'' Russell said, adding that the timing of a cool change would make the difference.
Between now and early next week, sea breezes wouldl help coastal regions avoid the full blast of heat "but in the north, there's just no reprieve at all," Russell said.
A maximum of 25C for Melbourne on Wednesday would give residents a break from the heat before the next cool change helped knock the heat down again to 26C next Monday, the bureau said.
The Country Fire Authority updated its fire-danger warnings for today, listing the Wimmera and the South-West as "extreme".
The Central area, which included Melbourne, Mallee, Northern Country and North Central regions was rated as "severe".
State control centre spokesman Paul Huggett said Victoria was entering the peak of the fire season just as the heat returned.
"Tomorrow [today] will be what we call the 'spike day'," Huggett said.
He said that given the hot and dry conditions of the last couple of weeks, most parts of the state ''are very dry and ready to burn''.
"Although all of the big fires that started during the last heatwave are currently controlled, we still have to keep a very active eye on them, considering tomorrow will be a very windy day,'' he said.
The cool change forecast for today evening will also pose a threat to firefighters, because temperature shifts often mean different fire activity.
Huggett advised parents to know where their children were at all times as they return to school, and for residents to consider their fire plans ahead of the heatwave.
"Tuesday in Victoria looks like a dangerous day [for bushfires]," Sharpe said.
"Then we'll have a few days without much wind until the Sunday, when we could see the winds picking up again."
Thursday may prove to be another challenging day, with the possibility of thunderstorms over mountain areas, the bureau's Russell said.
''That's the last thing you want." Russell said.
"You want significant rains. You don't want lightning involved on hot days.''
Unfortunately, there is little prospect of significant rain over south-eastern Australia for at least another week, Weatherzone's Sharpe said.
Fire authorities in SA and NSW remain busy battling fires mostly started by lightning during last week's spell of fierce heat.
On Monday, SA's Country Fire Service crews were working to contain an uncontrolled bushfire burning towards the small townships of Napperby and Nelshaby in the southern Flinders Ranges.
NSW's Rural Fire Service is also fighting six uncontrolled fires among 44 blazes burning across the state as of Monday.
"With conditions starting to warm, there's the potential for new fires to start," said Joel Kursawe, an RFS spokesman.
The previous heatwave was one of the most significant in history, the Bureau of Meteorology noted in a special climate statement released last week.
As of the end of last week, Australia was on course for its fourth-hottest January on record. The coming bursts of heat may lift that ranking even higher, Sharpe said.
While regions of northern Australia have had monsoonal or cyclonic conditions keeping a lid on temperatures, "there's still stacks of heat over the south", he said.
Nationwide, January 2013 was the hottest in more than a century of standardised records. The year as a whole was also Australia's hottest, easily eclipsing 2005, the bureau said earlier this month.
- The Age