Residents were told to take immediate shelter on Thursday as state emergency services issued a "red alert" for people in coastal areas.
The massive oil and ore ports of Karratha and Dampier are expected to take the brunt of the storm.
Spokesman Jim Cahill said: "The cyclone is basically very close and there are extreme winds and a lot of danger. If people haven't evacuated by now, it's probably too late."
Glenda was a category four cyclone, just one level below the maximum five, and was forecast to make landfall later on Thursday in the Pilbara, Australia's main iron ore producing region and the site of major oil and gas fields. The region has a population of about 10,000.
At 5am (2100 GMT Wednesday), Glenda was a "very dangerous, severe tropical cylcone" located about 185km northwest of Karratha, moving southwest towards the coast at 15km an hour, the Bureau of Meteorology said.
Gales up to 100km an hour and heavy rains were already lashing the Pilbara coast early on Thursday and were expected to increase to "very destructive gusts" of 250km an hour as the cyclone centre nears land, it said.
Glenda is expected to create a very dangerous storm tide and flooding in the region, which has already seen substantial rains in recent weeks, the height of the eastern Indian Ocean cyclone season.
Ahead of Glenda, mining and oil giants BHP Billiton, Rio Tinto, Santos and Woodside Petroleum shut down offshore rigs in the path of the storm and closed port operations in and around Karratha.
"At this stage, we are in full tie-down at the ports, which means basically we have sent all our ships out to sea and stopped all operations at the port"
Rio Tinto spokeswoman
Woodside and Santos sent floating oil rigs from their big Cossack and Mutineer Exeter oilfields out to sea away from Glenda's route.
BHP Billiton and Rio Tinto suspended all shipping of iron ore from its Pilbara mines, but were continuing mining operations.
A Rio Tinto spokeswoman said: "At this stage, we are in full tie-down at the ports, which means basically we have sent all our ships out to sea and stopped all operations at the port."
Glenda is due to hit just 10 days after a category five cyclone, Larry, caused widespread devastation in the country's tropical northeast.
Larry destroyed or damaged hundred of homes and wiped out banana and sugar cane crops, leaving a damage bill expected to top US$700 million. No one was killed.
The northwest Australian coast is known as "cyclone alley" and Glenda is the sixth tropical storm so far this season.