A 27-year-old jillaroo has died after collapsing while mustering cattle on horseback in searing 44.8C heat in the Pilbara.

Tiffani Phelps De Wildt fell ill on December 10 while working at Ashburton Downs station.

Colleagues said that she complained of exhaustion before they sat her in the shade of her horse and radioed her husband Corey for help.

He drove from the station and met them on the highway before racing toward hospital.

“She lost consciousness in the car,” her brother Brandon De Wildt told the ABC.

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“He stopped, took her out and gave her CPR. We know she said some words in Dutch … and her husband isn’t too good at Dutch.”

Paramedics found Ms Phelps De Wildt, who had moved to WA from the Netherlands six years earlier, unresponsive on the Paraburdoo–Tom Price Highway, about 30km from the nearest medical centre.

She could not be revived.

The Bureau of Meteorology recorded a maximum of 44.8C in nearby Paraburdoo that day — the hottest day of December 2025.

“What the paramedics said at the scene was that it could possibly be heat stroke,” Mr De Wildt said.

“She was advised not to go out but she really wanted to go for the animals.

“My sister is who she is — she loves being outside and she loves the animals.

St John WA deputy director of paramedicine Andy Bell said Ms Phelps De Wildt’s was an “absolute tragedy” and served as a warning at how working in extreme heat could be deadly.

“This is a classic case of somebody working in a very, very hot environment displaying signs of heat-related illness,” he told the ABC.

“Because of the tyranny of distance in rural WA, it’s very, very difficult for people to get the help they need in a timeframe that would be most appropriate.”

Mr De Wildt said his sister would be hugely missed.

“She was a wonderful person,” he said. “She had a really kind smile — one of those where, when you see her, you smile yourself.”

WA Police are preparing a report for the coroner. WorkSafe is investigating.