Diversified major Rio Tinto Group warned on Wednesday that its 2025 iron-ore output will likely land at the lower end of guidance as extreme weather disrupts operations in Australia’s Pilbara region.

While the miner maintained its full-year production guidance of 323-million to 338-million tons, it said first-quarter shipments dropped to 70.7-million tons – down 9% from the same period last year and 17% lower than the fourth quarter of 2024.

The decline follows the impact of four cyclones during the March quarter, which cost the company an estimated 13-million tons of production. Rio said mitigation efforts are under way to recover roughly half that loss, including rectification works and contracted mining services. The recovery plan will require an additional investment of about A$150-million.

“Pilbara iron-ore guidance remains subject to the timing of approvals for planned mining areas and heritage clearances,” Rio cautioned, noting that the system has “limited ability to mitigate further losses from weather if incurred".

The production setback leaves Rio vulnerable to losing its crown as the world’s biggest iron-ore producer. Brazil’s Vale on Tuesday maintained its guidance of 325-million to 335-million tons, the upper-end of which could mean it surpasses Rio should its production be at the lower-end of its guidance.

Despite the iron-ore challenges, Rio reported a strong performance in its copper division. Output rose 16% year-on-year to 210 000 t, although production dipped 8% from the prior quarter.

The Oyu Tolgoi underground mine and concentrator underwent maintenance in January and February. March marked a milestone at Oyu Tolgoi, with record monthly production in line with the mine’s ramp-up plan.

The underground operation continued to post material handling records, achieving an average of 28 000 t/d and peak rates of 45 000 t/d. Rio said Oyu Tolgoi was on track for more than a 50% increase in copper output this year, with growth weighted to the second half, when concentrator conversion is completed and a second primary crusher is operational. Long-term plans aim to deliver 500 000 t/y of copper (on a 100% basis) from 2028 through 2036.

In aluminium, Rio posted modest year-on-year gains in bauxite and alumina production, while aluminium output held steady. Bauxite output reached 14.97-million tons, alumina notched up 9.81-million tons, and aluminium remained unchanged at 829 000 t.

Commenting on the first-quarter performance, CEO Jakob Stausholm said, "We continued to see strong operational improvement with the Oyu Tolgoi copper mine and our bauxite operations delivering record months for production in March."

He also said Rio was making “good progress” in expanding its iron-ore operations, noting that first production was achieved at the Western Range project in the Pilbara. He also reaffirmed that the company’s high-grade Simandou project in Guinea “remains on track".