Temperatures in inland south-eastern Australia are set to climb into the low 40s on Thursday and Friday as a heatwave sweeps South Australia, Victoria and southern New South Wales.
The fire danger rating in inland districts around the Wimmera, Mallee and Riverina is expected to climb to catastrophic, putting additional strain on emergency services already battling dozens of fires in Victoria and South Australia.
An emergency warning was issued for an out-of-control bushfire at Devon North in the Tarra Valley in Gippsland, 229km south-east of Melbourne on Tuesday, one of about 10 fires burning around the state.
In South Australia, firefighters were working to contain two fires burning in the Mount Lofty Ranges area south-east of Adelaide.
The Bureau of Meteorology’s severe weather forecaster and fire weather expert, Claire Yeo, told Guardian Australia the fire danger would worsen as a low-intensity heatwave moved from Western Australia across to South Australia and Victoria, bringing temperatures in the mid-30s for capital cities and even hotter temperatures for inland regions.
In WA that heightened fire risk hit on Tuesday, with a catastrophic fire danger rating declared for parts of the Great Southern region near Esperance, 718km south-east of Perth. Three bushfires were burning out of control near Esperance on Tuesday afternoon and a fourth bushfire was burning near Albany, 481km to the west.
The temperature in Adelaide is expected to climb to 38C on Wednesday, dipping to 20C overnight before rising to 34C on Thursday and returning to 27C on Friday as a cooler change comes through.
Melbourne and Sydney will experience similarly hot weather – temperatures in Melbourne are forecast to peak at 34C on Friday, again with warm overnight temperatures of about 20C, while Sydney is expected to reach 39C on Friday.
Yeo said the low-intensity heat wave, combined with dry fuel loads and forecast of gusty northerly winds for later in the week, would see areas like the Mallee and Wimmera in Victoria, which were already at a fire danger rating of severe on Tuesday, climbing to extreme or even catastrophic.
The catastrophic level was introduced after the fatal Black Saturday bushfires in 2009. In catastrophic or code red fire conditions, the Country Fire Authority advises anyone living in a fire risk area to leave before a fire starts, warning that houses are neither designed nor constructed to survive a fire in those conditions.
Yeo said the 2015/2016 Victorian fire season could be compared to the 2006/2007 fire season, which saw one of the longest continually running bushfires in the state’s history. The fire in the Victorian Alps started on 1 December after a series of dry lightning strikes and burned for 69 days, wiping out a million hectares.
“This year hasn’t been as dry as 2006, but it is comparable, it’s the next driest year,” Yeo said.
Yeo said a drop in rainfall was to be expected under El Niño conditions. The bureau previously said the El Niño in the Pacific was one of the three strongest ever recorded, meaning its drying effect on Australia would be comparable to the devastating droughts of 1997-98 and 1982-82.
She said fire forecasters were now able to accurately predict conditions that might affect a fire – like the timing of wind changes and the likelihood of dry lightning strikes – but in severe fire danger conditions the question was not when a fire would start, but where.
“What makes this level of fire danger days difficult is trying to predict where a fire might start,” she said.
“We might have a map of predicted lightning strikes kilometres apart, but we don’t know which one is going to spark.”
