Much of south-east Australia will swelter through a heatwave over the weekend that is expected to exceed 40C in some places, bringing extreme fire danger before a cool change comes through. Melbourne was expected to peak at 38C on Saturday, reaching 37C on Sunday and dropping to 22C by Monday as the cool change brings widespread showers. Farther inland, temperatures could reach the low 40s through northern Victoria and along the Murray River at the weekend. In Victoria, Mildura could reach 41C on Saturday and Sunday, while Shepparton was forecast to hit 40C on Sunday. Sign up for Guardian Australia’s