Australia Weather News

Southern Australia will collectively bake this week through the most intense spell of heat in years as temperatures soar up to 15 degrees Celsius above the mid-summer average.

At its peak, daytime maximums will hit the mid-40s across multiple days in a broad stretch of the country from northern WA to the south-east inland — coming within a few degrees of all-time records.

However, milder coastal regions will also sweat through sweltering temperatures, peaking at 44C in Western Sydney, 44C across northern Adelaide, and 42C in Melbourne.

Exceptionally muggy nights will accompany the hot days to produce oppressive conditions, which, combined with the longevity of the event, has triggered a severe-to-extreme heatwave warning across the majority of SA, Victoria, and NSW.

The fire risk also poses a serious threat as the searing heat arrives with low humidity and twin bands of fresh-to-strong winds.

Here is a day-to-day breakdown of the weather for the remainder of the week for south-east states:

Wednesday

The peak of the heatwave will start on Wednesday as north-westerly winds combine with sunny skies and a compression of air near the surface (more details in the explanation at the end of the article).

The map below shows the expected temperatures through the mid-afternoon, which should 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, and if Melbourne's official weather station at Olympic Park climbs above 40.5C it will be the city's highest maximum in six years.

Wind speeds will also freshen in SA and Victoria, leading to an extreme fire danger rating in numerous districts.

A cooler change will then reach the coastal fringe of SA and western Victoria this afternoon, before edging north to Adelaide and Melbourne this evening.

Thursday

Following Wednesday's change, Thursday will be cooler in south-west Victoria and coastal SA. However, the change will weaken and stall just inland from the coast.

This will allow the heat to further intensify across the remainder of southern Australia as the very hot and dry north-westerly airstream continues.

Peak afternoon highs could reach 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.

For many locations, Thursday could be the hottest day in years, including forecasts of:

The strongest winds on Thursday will also shift slightly north, leading to a few pockets of extreme fire danger in northern Victoria and possibly the mid-north region of SA.

A cool wind change will reach Gippsland this afternoon. However, the hot north-westerly winds will win the battle in the short-term and spread back to the Victorian coastline by Friday.

Friday

Friday is shaping up to be yet another scorcher for south-east Australia, with temperatures above 40C from northern SA, through much of Victoria to the eastern inland of NSW.

By Friday, multi-day hot streaks will also be notable, including possibly Mildura’s first run of three consecutive days above 44C in eight years, while Albury and Wagga Wagga can expect three consecutive days above 40C for the first time in six years.

Another cool change, this one stronger, will reach the SA coast, which should then spread to western Victoria in the evening, and Melbourne near midnight.

A burst of strong winds should develop ahead of the change, which could gust up to 90 kilometres per hour on the Victorian ranges, resulting in a widespread 'extreme' rating across the state, along with numerous parts of SA.

Saturday

The weather will become more mobile on Saturday as a cold front sweeps through Tasmania and Bass Strait.

This system will drive the cool change further inland, leading to a major drop in maximums by as much 18C in SA and Victoria compared to Friday.

North of the change, 40C-plus maximums will continue across north-east SA and NSW, including a forecast high of 44C in Penrith, Western Sydney's hottest day in six years.

Canberra is forecast to hit 38C on Saturday for the third consecutive day — a run of heat last recorded in our capital back in 2019.

Saturday is also likely to bring elevated fire danger to NSW, with pockets of extreme danger in the state's south-east.

The welcome southerly change will surge north up the southern NSW coast in the afternoon, and at this stage is predicted to reach Sydney and Canberra during the late evening.

Sunday

By Sunday, 40C temperatures (across southern Australia) will be confined to northern inland NSW and the far north-east corner of SA.

Heatwave classifications and why this event is 'extreme'

While the term heatwave is thrown around loosely, the Bureau of Meteorology's official definition is based on unusually hot weather averaged across a three-day period, including both night and daytime temperatures.

The equation used to classify a heatwave is complex, but essentially calculates the threat to human health based on how severely temperatures are departing from a region's recent weather and long-term climate — therefore capturing the effects of acclimatisation.

The majority of heatwaves are low intensity. However, 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.

So why is this week's heat more severe than a typical summer hot spell? 

The intensity and longevity of the current hot weather event are the result of multiple factors occurring simultaneously: