A large portion of Western Australia is currently under the grip of a heatwave, with maximum temperatures soaring above the already scorching January average in many regions.

The BoM defines a heatwave as "when both the minimum and maximum temperatures are unusually hot for 3 days or longer” – and that’s the scenario right now even in famously hot parts of WA like the Pilbara region.

Indeed, the run of extreme heat is set to last much longer than three days.

Australia’s "hottest town" much hotter than average

Marble Bar bills itself as "Australia’s hottest town", although exactly how you define that is up for debate. For example, two other towns jointly hold Australia’s highest recorded temperature of 50.7°C – Oodnadatta in SA and Onslow in WA – while Marble Bar’s hottest recorded day was "only" 49.3°C.

But for consistent heat, it’s hard to beat Marble Bar. The small mining outpost with a population of around 900 has an average maximum temperature of 42.1°C in December (the hottest month) and 40.9°C in January, in records dating back to the year 2000.

Marble Bar’s maximums in the current heatwave are much hotter than the January average. Wednesday‘s maximum was 44.1°C. This Thursday is predicted to reach 45°C, followed by a run of days expected to peak at 45°C, 46°C, 43°C, 46°C, 47°C and 47°C again by next Wednesday.

Image: The Marble Bar Roadhouse, WA, where cold drinks are probably quite popular. Source: iStock/Adrian Wojcik.

Back in the summer of 2023/24, Marble Bar endured a run of 26 days where the mercury reached at least 43°C. On six of those days, the mercury hit 47°C or higher.

So the current heatwave is not yet in record-breaking territory in terms of its extreme temperatures or its duration, but it’s nonetheless a very significant weather event

And as mentioned, the heat extends well beyond the Pilbara. WA forecast districts where heatwave conditions are occurring this week also include the Kimberley, North Interior, South Interior, Gascoyne, Central West and Southern Wheatbelt.

Even the Lower West (where Perth is located) and South West have low-intensity heatwave warnings current, although by far the most severe heat is further north and further inland.

Image: The current heatwave is already underway, but as shown in the three-day chart from this coming Sunday, January 18, it will last well into next week.

What's causing this WA heatwave?

Interestingly, the same easterly winds bringing moist conditions to eastern parts of NSW and Victoria are partly responsible as they circulate around a strong high pressure system centred over the Bight. Those winds are then drying out and warming up as they cross the arid interior of the continent heading west.

"A persistent heat trough over the Pilbara and Kimberley is also a factor, allowing significant heat to build over the northern half of the state," Weatherzone meteorologist Angus Konta adds.

"This heat is transported south as troughs extend down the west coast, allowing for the surges of heat for southern districts."

Perth is heading for a maximum of 36°C this Thursday, then a string of days with highs within a few degrees of the January average of 31.4°C, before a fresh surge of heat next Tuesday lifts maximums towards 40°C in the city and suburbs.