A code red has been issued in South Australia as temperatures hit 42C in the state’s capital, while firefighters battling wildfires in New South Wales established containment lines ahead of an expected heatwave.

South Australia last week had 86 homes destroyed after wildfires flared, as its capital Adelaide endured a heatwave peaking at a sizzling 46C.

There was respite during the Christmas period, but oppressive conditions returned on Friday and are set to continue until Monday.

The heatwave has prompted the South Australian government to declare a code red, which aims to ensure the homeless are kept cool and hydrated. Services include shelter options and additional food services.

“Keeping vulnerable South Australians safe and well in the extreme heat forecast over the next few days is our priority,” South Australian human services minister Michelle Lensink said.

The fire danger rating was severe in Adelaide, while the rest of the state was mostly between high and very high.

About 1,300 firefighters in New South Wales on Friday established containment lines in cooler conditions, but about 70 fires continued to burn across the state with almost half of them not contained.

New South Wales Rural Fire Service Commissioner Shane Fitzsimmons said: “Because these fires are large, they’re complex and they’re very prone to the elements. Once these weather conditions turn around, we know we’re going to see increased fire activity.

“So they’re just giving their all to shore up protection and trying to consolidate and contain them as much as they can.”

Authorities are bracing for conditions to deteriorate, with Sydney forecast to hit 31C on Sunday and 35C on Tuesday. The city’s western suburbs could reach 41C on Sunday.

Fire danger ratings remained very high in north-western New South Wales, and high in Sydney.

About 12.35 million acres of land have burned nationwide over the past few months, with nine people killed and more than 950 homes destroyed. New South Wales, the country’s most populous state, has received the brunt of the damage, with around 850 homes razed.

Meanwhile, defence minister Linda Reynolds said beleaguered prime minister Scott Morrison has had discussions with state premiers over how to financially support volunteer firefighters.

Mr Morrison, who has been under pressure since taking a much criticised family holiday to Hawaii during the wildfire crisis, announced on Tuesday that volunteer firefighters from the federal public sector will receive paid leave entitlements.

“He’s been discussing (financial support) with the premier of New South Wales and other state and territory leaders,” Ms Reynolds told reporters in Perth.

“So the prime minister is looking at this issue further on how we can provide targeted support in these extreme circumstances, so that our volunteers get the support they need to keep volunteering.”