Australia is set to endure its worst heatwave since the deadly 2019-20 bushfires. The Bureau of Meteorology warned that temperatures will climb over 45C in parts of the country, causing extreme fire risks and widespread heat stress. The scorching heat began in Western Australia and will spread to South Australia, New South Wales, and Victoria starting Tuesday. Senior forecaster Dean Narramore said, "Our main concern is the three-day period running Wednesday through Friday. We’re likely to see extreme heatwave conditions over a huge part of NSW and northern Victoria, practically everywhere between Melbourne and Sydney and extending well inland. It is looking like … the most significant burst of heat for south-eastern Australia, particularly in terms of multiple days in a row of mid-40 temperatures, since the summer of 2019-2020." Millions of residents in NSW and Victoria should prepare for intense heat, including low 40s temperatures even in coastal cities like Adelaide and Melbourne. Fire dangers will peak at extreme levels in South Australia, Victoria, and inland NSW, with total fire bans expected across much of the country. Electricity grids face heavy pressure as air conditioners run nonstop. Matthew Sweeting from energy supplier Ausgrid warned, "There is an increased risk of unplanned outages during prolonged heatwave conditions, due to an increase in demand on the grid." The Bureau defines a heatwave as three or more days of above-average temperatures. Australia saw its fourth-warmest year on record in 2025, with temperatures 1.3C above average, following its second warmest in 2024. Climatology expert Nadine D’Argent noted, "South Australia and Western Australia both recorded their third-warmest years. Between January and March, and between October and December, large parts of Australia experienced heatwave conditions, reaching extreme severity at times." The climate crisis continues to increase the frequency and strength of such dangerous heatwaves and extreme weather events.