A prolonged and intense heatwave impacted southeastern Australia over several weeks, characterized by record-breaking temperatures, widespread bushfire danger, and disruptions to infrastructure and events.
Temperature and Heatwave Records
A slow-moving, stationary high-pressure system created a "heat dome" over the region, trapping hot air and forcing it downwards, which rapidly warmed the air mass. This system was positioned further south than typical and obstructed the usual eastward flow of weather, leading to an extended period of extreme heat.
Several towns and cities recorded all-time high temperatures:
- South Australia: Andamooka and Port Augusta each officially recorded 50.0°C. These were the 8th and 9th instances of 50°C in Australia's history. Ceduna reached 49.5°C on Monday and Wudinna reached 48.6°C, both being their hottest days on record.
- Victoria: The state recorded a high of 48.9°C in Walpeup and Hopetoun, a new state record. Mildura reached 49°C and Swan Hill 48°C. Melbourne reached 45.6°C.
- New South Wales: Pooncarie reached 49.7°C, and Ivanhoe reached 48°C. Trangie (47.3°C) and Dubbo (46.1°C) recorded their hottest days in decades.
The heatwave was notable for its duration, with vast inland areas experiencing at least seven to eight consecutive days above 40°C.
Mildura faced three consecutive days above 44°C, and towns like Wagga Wagga and Albury recorded seven consecutive days at or above 40°C for the first time since 1939. Overnight minimum temperatures remained exceptionally high, with a minimum of 34.2°C recorded in Marree, SA, and several towns staying above 30°C for over 100 consecutive hours.
Fire Danger and Public Safety Measures
The combination of extreme heat, low humidity, and strong winds created widespread extreme and catastrophic fire danger.
- Victoria: Total fire bans were declared for multiple districts, including the Mallee, Wimmera, South West, Central, and Northern Country regions. Fire danger was predicted to peak on Friday with extreme conditions widespread across the state. Authorities warned of the potential for dry lightning. The state was still recovering from recent major fires that burned over 400,000 hectares and destroyed 1,500 structures.
- South Australia: Catastrophic fire danger was declared for the Eastern Eyre and Yorke Peninsulas, with extreme ratings in twelve other regions. Total fire bans were in effect for all areas except the Adelaide metropolitan area. A bushfire burned 700 hectares on the Fleurieu Peninsula.
- New South Wales: Extreme fire danger was forecast for the state's south-east and other districts.
Infrastructure and Event Disruptions
- Power Outages: SA Power Networks reported over 100,000 properties experienced power outages since January 24, with approximately 38,000 on Thursday night alone. Outages were linked to heat-related issues such as blown fuses and fallen trees.
- Transport: V/Line in Victoria implemented a revised timetable for heat-affected areas, reducing train speeds to prevent track buckling. The men's Tour Down Under cycling race in South Australia was modified: the start time was moved earlier, the distance reduced from 176 km to 131 km, and the final climb of Willunga Hill was removed. The Aus Lights Parade was cancelled.
- Consumer Spending: A study of 200 million bank transactions showed that during heatwaves, spending shifted to evening hours. Daily daytime spending declined, while evening spending increased by approximately 5% between 6pm and 11pm.
Temperature Forecasts and Outlook
- Wednesday: The heatwave intensified with temperatures reaching 40-45°C across western NSW, much of Victoria, and nearly all of SA. Cooler air reached coastal areas of SA and western Victoria by evening.
- Thursday: The cooling effect diminished inland, with peak temperatures of 46-47°C forecast for the Mallee, eastern SA, and south-west NSW. A cool change reached Gippsland in the afternoon.
- Friday: The main danger day for fires. Temperatures exceeded 40°C across northern SA, much of Victoria, and eastern inland NSW. A stronger cool change reached the SA coast and western Victoria by evening.
- Weekend: A cold front moving through Bass Strait brought a significant temperature drop of 10-18°C to SA and Victoria. The heat shifted eastward, with Sydney reaching 39°C on Saturday and Canberra 38°C.
Scientific and Health Context
The Bureau of Meteorology defines a heatwave as three or more consecutive days of unusually high temperatures for a specific location. Heatwaves are Australia's deadliest natural disaster, with the 2009 event resulting in over 400 fatalities.
New research indicates that deadly heat stress conditions are occurring at temperatures and humidity levels previously considered survivable.
The HEAT-Lim model suggests that environmental heat stress thresholds may be lower than the long-held wet-bulb temperature limit of 35°C, particularly for older individuals. Vulnerable populations include the elderly, young children, pregnant individuals, those with chronic health conditions, and those with limited access to air conditioning.
Broader Climate Context
Multiple sources noted that global warming is contributing to more frequent, longer, and more intense heatwaves. A study projected that extreme heat events could occur up to four times more often in eastern and southern Australia with up to three degrees of global warming. Economic impacts were projected to reach up to $400 billion per year in Australia due to lost work time and effects on industry and infrastructure.