'Extremely dangerous': how much of the heat can western Sydney bear?

Anyone who’s lived in western Sydney in summer will tell you the days of searing heat and burning bitumen feel very different from the rest of the city.

No matter what time of year, it’s generally hotter in the west. Over the past 30 years, the average yearly maximum temperature recorded at Parramatta was 23.7C, compared with 22.8C at Observatory Hill, just across from the Harbour Bridge. But those figures hide the extent of the disparity in the summer months. In January, the average daily maximum in Penrith – Sydney’s western limit at the foot of the Blue Mountains – is 31.2C, compared with 27C in the city centre.

That can mean extreme temperatures, such as on 4 January 2020, when Penrith was the hottest place on Earth at 48.9C. Or on 7 January 2018, when Penrith recorded the hottest temperature in nearly 80 years, at 47.3C.

And a lack of shade and large expanses of heat-trapping asphalt and concrete in smaller localities can make the conditions even worse.

The causes of the discrepancy – both natural and human-influenced – are well known, but with more days of extreme heat expected due to the effects of climate change, there is little agreement on what can be done to make life in summer more bearable for the majority of Sydney’s population.

Dr Sebastian Pfautsch, an expert in urban heat and senior research fellow at Western Sydney University, says the first and most obvious reason for the heat in the western suburbs is that they do not benefit from a sea breeze.

“The sea breeze stops [at] about the Olympic peninsula [near Homebush] – that’s about as far up the river it goes before being blocked off,” Pfautsch says.

But the far west is also particularly affected by the city’s geomorphology – the lowest point of the city is at the Nepean River, at the base of the Blue Mountains.

“It’s actually like a pan, where the lowest depression is towards the river. That’s the lowest point. When you drive down that highway and you feel you’re driving down, it’s like a depression that holds hot air,” Pfautsch says.

Hot air is trapped in the region, making suburbs in the triangle between Blacktown, Windsor and Penrith the hottest parts of the city.

Parts of the west also receive up to 400mm less rain a year than the east of the city.

“That leads to less water in the system that can be evaporated or transpired by vegetation,” Pfautsch says. “And then this cooling effect that you get from the evapotranspiration is just not as big as in other parts of Sydney.”

These natural factors have been made worse by the destruction of bushland across the west and its replacement with buildings and roads, which Pfautsch summarises as a “mass conversion from green to grey”.

“Now we have a massive conversion … from green infrastructure to grey infrastructure, from pastures and meadows in agricultural land into shopping centres, car parks and residential suburbs.”

Without vegetation that can convert solar radiation into biomass, the region has little to no outlet for the heat, instead absorbing it into the roads and buildings, he says.

“When you previously had a paddock with some remnant vegetation, it would have kept relatively cooler, because it wouldn’t have stored as much energy.

“And because water would be able to seep into the ground, it became plant-available and would have been evapotranspirated, which again provides you cooling.”

What that all means is that western Sydney residents face increasingly long runs of dangerous temperatures in summer.

In 2018-19, one street in Parramatta recorded 13 days of 40C or higher, and in 2017 the suburb recorded 28 days above 35C.

Our bodies are not built to deal with these regular days of extreme heat, Pfautsch says.

“People really need to understand that it is extremely dangerous to live in these kind of temperatures because the body struggles to cool down from those extremes.”

Prof Diana Egerton-Warburton, an emergency medicine physician, says a range of dangers come from exposure to extreme heat, particularly for the young and the very old.

There are the direct consequences, such as heat stroke and exhaustion, but also serious indirect impacts, she says.

“Heat causes a lot of cardiovascular complications, such a stroke and heart attack,” Egerton-Warburton says.

“When the temperature is particularly high, particularly overnight, there are actually well defined and researched thresholds where the rates of heart attack and mortality increase.”

Extreme heat can also affect the brain and kidneys.

Charles Casuscelli, the chief executive of the Western Sydney Regional Organisation of Councils (WSROC), says the heat is an existential threat to the future of the region.

“This is a liveability issue. It’s not about being comfortable, it’s about asking if I can or can’t live in western Sydney,” he says.

One challenge for local authorities aiming to make the region’s environment more tolerable is working out where to start.

Some initiatives focus on the immediate task of mitigating the worst effects of extreme days by providing cooler places for recreational and other activities.

Blacktown City council has implemented a “heat refuge network” that opens community-run air-conditioned spaces for vulnerable residents during an extreme heat event.

The Parramatta River Catchment Group, an alliance of councils, government agencies and community groups, has been working to clean and transform the Parramatta River into a series of swimming spots.

And in 2020, Cumberland council introduced a world-first UV Smart Cool playground at the Merrylands Memorial Park to protect children from heated play equipment.

But in the longer term, changes to land use and development will determine whether living in western Sydney becomes more bearable for its growing population.

In 2018, WSROC developed its Turn Down the Heat Strategy. Casuscelli says it is essential that heat mitigation is included in planning and development, from using appropriate colours to allowing space for vegetation and trees.

“We are still not designing our homes with the right elements to minimise the amount of heat that it absorbs,” he says.

“Why in heaven’s name are we still building homes in western Sydney with dark colours? That is just dumb, dumb and dumber.”

The New South Wales premier, Gladys Berejiklian, announced in December that 40,000 trees would be planted across greater Sydney, as part of two funding streams: Cooler Suburbs and Green Innovations.

The initiatives will provide 29 councils with more than $8m to support tree planting, but Casuscelli says the focus needs to expand from just trees.

“I am almost sick to death of how much focus everyone seems to be having on planting more and more trees to try and solve this problem, especially in western Sydney,” he says.

Pfautsch says authorities need to consider every element of community life in order to build sustainable and heat-resistant neighbourhoods.

He suggests a complete rethink of building practices, including apartment blocks that go partially below ground.

“We need to move away from just building one single freestanding dwelling next to the next to the next to the next to the next,” he says.

“But the fear there is, of course, that people don’t want to live in apartments because, when I look at apartments, we’ve designed them very badly over 30 or 40 years.”

Pfautsch says apartment blocks designed for comfort and not just to fit more people in can also be energy efficient, and would allow more space for parks and recreational spaces.

“A different type of life can be offered to those living in western Sydney,” he says. “But we need to be innovative, be radical.”




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