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Fire and snow: Australia's chaotic first week of summer

Source Weatherzone Mon 01 Dec 2025

The opening week of summer will feature a dynamic mix of weather across Australia, with extreme fire danger in multiple states, temperatures soaring to the high-40s and a burst of unseasonable snow. An unusual weather pattern will become established over Australia in the opening days of summer, featuring a large high pressure system centred much further north than usual for this time of year. This vagrant high pressure system will drive two contrasting air masses over Australia in the opening days of summer: A large pool of hot air will be pushed over Australia’s west A much cooler air mass will spread across the country’s southeast The map below, which shows Monday’s forecast maximum temperatures across Australia, highlights the contrasting temperatures on the first day of summer. Image: Forecast maximum temperatures in Australia on December 1, 2025. Source: Weatherzone. Cold in the southeast Anyone waking up to the first day of summer in southeastern Australia would have noticed that it was unusually cold for early December. This chilly start to the season was caused by a cold Southern Ocean air mass being driven across the country’s southeast ahead of the approaching high pressure system. Temperatures dropped below 0°C in parts of NSW, Vic and Tas early on Monday morning and some places are likely to have their coldest first day of summer on record due to this unseasonable burst of cold weather. Impressively, this system’s low temperatures have allowed snow to settle on the high mountains in southeastern Australia, giving anyone willing to hike to higher altitudes a chance of some rare Australian summer skiing. Heat in the west While parts of southeastern Australia have shivered trough the start of summer, those living in the west are dealing with intense heat and Extreme fire danger. A large pool of hot air is being pushed over western and northwestern Australia by the high pressure system. Perth is forecast to reach 37°C on Monday and Geraldton had already exceeded 40°C by 11am. Unfortunately, this heat is elevating fire danger ratings in parts of WA, with Extreme fire danger forecast in the Midwest Coast, Midwest Inland, Lesueur, Yarra Yarra and Swan Inland North districts. On Monday morning, emergency warnings were in place for fires burning around Geraldton and total fire bans extended from around Kalbarri to near Perth. Heat spreading east The hot air that is targeting WA on Monday will spread to other areas of Australia later this week as the high pressure system drifts over southeastern Australia and eventually off the country’s east coast. Image: Forecast 850 hPa temperature and mean sea level pressure at 5pm AEDT on Friday, December 5. Source: Weatherzone. The hot air will drift over southern Australia in the middle of the week before intensifying over central and eastern Australia later in the week. Adelaide is forecast to reach the low to mid 30s on Wednesday and Thursday Melbourne, which only reached the mid-teens on Monday, is predicted to hit 29°C on Wednesday and 33°C on Thursday Hobart should reach the mid to high 20s on Wednesday and Thursday Canberra could exceed 30°C for three days between Thursday and Saturday Sydney could also have three days over 30°C starting from Thursday, possibly reaching 37°C in the city and 42°C in the west on Saturday Brisbane will see a few days in the low 30s towards the end of the week Image: Daily forecast for Penrith, NSW in the Weatherzone app. By the weekend, the hot air mass will be extending from WA to NSW, with 40°C heat extending more than 4,000 km across the country. - Weatherzone © Weatherzone 2025