Australian authorities have issued extensive heatwave warnings for large parts of the country as millions of residents and visitors observe Australia Day.

The Bureau of Meteorology forecasts temperatures soaring into the high forties Celsius in southern states including Victoria and South Australia, with many inland regions approaching or potentially exceeding long-standing heat records.

South Australia recorded temperatures up to forty-eight point five degrees Celsius over the weekend.

Many of the alerts will remain in effect into midweek as an intense dome of hot air persists.

The extreme heat has prompted the cancellation of several Australia Day celebrations and public events on safety grounds.

Organisers in Adelaide suspended a planned parade and light show, emphasising that community wellbeing is the priority amidst forecasts of severe conditions.

Heat warnings extend beyond the south.

New South Wales, Queensland, Tasmania, the Northern Territory and the Australian Capital Territory are all under varying levels of alert.

The bureau’s heatwave advisory system, which factors in prolonged high daytime and overnight temperatures that place strain on health services and infrastructure, indicates severe to extreme conditions across much of the mainland.

Queensland recorded its hottest day of the year, with multiple inland locations exceeding forty degrees Celsius.

Energy demand surged, contributing to power outages in parts of Brisbane and nearby areas.

Severe thunderstorm warnings were also issued for several regions, including Ipswich and the Gold Coast.

In the south-east, prolonged heat has significantly elevated bushfire risk.

Total fire bans are in force in several regions, while emergency services in Victoria ordered evacuations in the Otways after a major fire breached containment lines.

Crews continue to battle blazes under difficult conditions, with forecasts indicating continued extreme heat.

Authorities are urging residents, particularly older people, children and those with health vulnerabilities, to take precautions, remain hydrated and follow official advice.

Meteorologists say some relief may arrive later in the week if weather patterns shift, but conditions remain dangerous in the immediate term.