"The mine and rail operations continue to operate as normal but ship loading has now stopped," Rio Tinto spokesman Bruce Tobin said in a statement.
BHP spokeswoman Fiona Hadley said the company was "progressively securing port, rail and mine infrastructure and tying-down equipment".
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Fortescue Metals said it was preparing in line with its cyclone procedures.
The northwest is also home to two of Australia's biggest gas production facilities, Woodside Petroleum's Northwest Shelf and Pluto liquefied natural gas (LNG) plants.
While declining to say whether production facilities had slowed or staff had been moved, Woodside spokesman Daniel Clery said the company was "taking all necessary steps to safeguard its people and assets".
Australia is the world's largest producer of iron ore and exports from Port Hedland were 28.1 million tonnes in November, just off October's all-time peak of 29.0 million and 29 percent higher than in November last year.
(Read more: Developing Asia key for iron ore trade: Fortescue CEO)
The majority of the ore is shipped under contract to steel mills in China.
Australia can expect an average cyclone season running from Nov. 1 to April 30, with up to 11 storms. Cyclones are categorised from 1 to 5, with 5 being the most severe and bringing wind speeds of more than 280 km (175 miles) per hour.