Key Takeaways
- A severe-to-extreme heatwave warning has been issued for southern Australia, with temperatures expected to soar up to 15 degrees Celsius above the mid-summer average.
- Daytime maximums will hit the mid-40s across multiple days, coming within a few degrees of all-time records.
- The heatwave will be accompanied by exceptionally muggy nights, producing oppressive conditions.
- The fire risk poses a serious threat, with low humidity and twin bands of fresh-to-strong winds.
- A cool change is expected to reach the coastal fringe of SA and western Victoria on Wednesday, but the heat will intensify across the remainder of southern Australia.
Introduction to the Heatwave
Southern Australia is expected to experience a severe heatwave this week, with temperatures soaring up to 15 degrees Celsius above the mid-summer average. The heatwave will affect a broad stretch of the country, from northern WA to the south-east inland, with daytime maximums hitting the mid-40s across multiple days. This will come within a few degrees of all-time records, making it one of the most intense heatwaves in years. The heatwave will also affect milder coastal regions, with temperatures peaking at 44C in Western Sydney, 44C across northern Adelaide, and 42C in Melbourne.
Day-to-Day Breakdown
The peak of the heatwave will start on Wednesday, with north-westerly winds combining with sunny skies and a compression of air near the surface. Temperatures will peak at 40C to 45C through the western half of NSW, much of Victoria, and nearly the whole of SA. Both Adelaide and Melbourne are likely to see their hottest day of the week on Wednesday, reaching the low 40s. On Thursday, the heat will intensify across the remainder of southern Australia, with peak afternoon highs reaching up to 46C to 47C in the Mallee, eastern and northern SA, and south-west NSW. The heatwave will also become more severe across eastern NSW, with the first day of 40C-plus temperatures possible just inland from the coast.
Fire Risk and Heatwave Classifications
The fire risk poses a serious threat, with low humidity and twin bands of fresh-to-strong winds. The strongest winds on Thursday will shift slightly north, leading to a few pockets of extreme fire danger in northern Victoria and possibly the mid-north region of SA. The heatwave classifications are based on unusually hot weather averaged across a three-day period, including both night and daytime temperatures. The majority of heatwaves are low intensity, but this week’s temperatures, both minimums and maximums, are high enough to pass ‘severe’ or ‘extreme’ heatwave thresholds. This indicates precautions should be taken to keep cool, particularly for the vulnerable, although at the highest end of the scale, a heatwave can even be detrimental to otherwise healthy people.
Causes of the Heatwave
The intensity and longevity of the current hot weather event are the result of multiple factors occurring simultaneously. A north-westerly airstream is carrying a very hot and dry desert air mass into southern states. A slow-moving high-pressure system in the Tasman Sea will maintain the surface pattern for several days. An upper high has formed over southern states, pushing air towards the ground, forcing compression, and even higher temperatures. Skies are clear, allowing for peak solar heating from sunlight. These factors combined have created a perfect storm of heat, making this week’s heatwave one of the most severe in years.
Conclusion and Weekend Forecast
The heatwave will continue to affect southern Australia throughout the week, with temperatures remaining high until a cool change reaches the region on Saturday. The cool change will bring a major drop in maximums, with temperatures plummeting by as much as 18C in SA and Victoria. The heat will peak in eastern NSW on Saturday, with temperatures reaching up to 44C in Penrith, Western Sydney’s hottest day in six years. By Sunday, 40C temperatures will be confined to northern inland NSW and the far north-east corner of SA, bringing an end to the severe heatwave. The cool southerly change will spread through most of NSW by Sunday, bringing relief to the region after a week of intense heat.