Australia is set for wildly different weather on Christmas Day, Thursday. Perth will swelter at 41°C and Brisbane will feel hot at 35°C, making them the hottest capital cities. Meanwhile, Melbourne and Hobart will be chilly with highs of 17°C and 16°C. Senior meteorologist Jonathan How told AAP, "If Melbourne only reaches 17C, it will be Melbourne’s coldest Christmas Day since 2006." He added, "Quite the extremes across both ends of the country." Melbourne could see a morning shower and western Tasmania may get wet weather, with "some light snow flurries about the elevated country on Christmas morning," How said. Brisbane will be “very muggy” and might face afternoon showers or thunderstorms. Storms and rain are forecast from the Sunshine Coast to Cairns, across the Northern Territory, and the Kimberley region in Western Australia. Darwin and Cairns expect temperatures in the low 30s°C. Parts of WA's Pilbara could hit highs in the low to mid 40s°C. Adelaide will enjoy milder weather with 25°C on Christmas and 29°C on Boxing Day. Sydney and Canberra will have comfortable temperatures in the mid-20s°C. The big temperature difference comes from a high-pressure system over the Great Australian Bight. "It just comes down to timing and unfortunately the coolest day of the week coincides with Christmas Day across Victoria and Tasmania," How said. Conditions will warm afterward, with Boxing Day set to be dry and sunny for the MCG Test match in Melbourne. Heatwaves continue across eastern and north-eastern NSW and southern Queensland. Western Sydney suburbs like Penrith and Richmond could see lows in the 40s°C. Fire bans are declared Sunday in five NSW districts and Victoria’s Mallee. Severe thunderstorm warnings cover parts of Victoria’s east and north-east and western NSW. Areas like Mildura, Swan Hill, Euroa, and Shepparton are warned to prepare for heavy rain, damaging winds, and possible tornadoes. Broken Hill and nearby towns could face large hailstones and strong storms.