Tropical Cyclone Yasi has been upgraded to Category 5 strength — the maximum rating — as it barrels towards the coast of northeastern Australia, prompting the premier of Queensland to warn of "catastrophic" damage to come.

A weather satellite image shows tropical Cyclone Yasi in the Coral Sea approaching the coast of Australia on Feb. 1. (Japan Meteorological Agency/Reuters)

Tens of thousands of people have already fled the path of what is expected to be the most devastating storm ever to hit the region, and possibly the country. Winds could reach upwards of 320 km/h, said CBC meteorologist Michelle Leslie.

The storm could take 24 hours once it hits land before it begins to weaken, Leslie said.

Yasi is forecast to make landfall around 10 p.m. local time Wednesday or early Thursday, according to Australia's Bureau of Meteorology. Hospitals have been evacuated, with patients in the storm's path in the far northern city of Cairns airlifted about 1,700 kilometres south overnight to Brisbane.

Queensland Premier Anna Bligh urged residents to consider the cyclone life-threatening.

"We are facing a storm of catastrophic proportions in a highly populated area," she told reporters. "What it all adds up to is a very frightening time. We're looking at 24 hours of quite terrifying winds, torrential rain, likely loss of electricity and mobile phones."

Airlines arrange extra flights for tourists

Those living in low-lying areas were particularly vulnerable and are being urged to flee, Bligh said. More than 9,000 residents in coastal and low-lying areas were ordered to evacuate in anticipation of storm surges that could exceed two metres and cause flooding.

Cairns, a city of some 164,000 people and a tourist gateway for its access to the Great Barrier Reef, was due to bear the brunt of the storm.

"We're in the process of packing up boxes … the dogs and the pet snake and getting out of here," Cairns resident Melissa Lovejoy told the Australian Broadcasting Corp.

The family left their home to find shelter further inland at a friend's home.

The Cairns airport was scheduled to close on Wednesday in advance of Cyclone Yasi, and airlines were arranging extra flights on Tuesday night to accommodate fleeing tourists.

An earlier storm, Cyclone Anthony, landed in Queensland early Monday, but quickly fizzled out after uprooting trees and damaging power lines.

The more powerful Cyclone Yasi is forecast to be much larger, with a storm front more than 500 kilometres wide, forecasters said.

Up to a metre of rain could fall on some coastal communities, even as many parts of Queensland state continue to recover from tropical deluges that began in November and caused significant flooding, killing 35 people and damaging some 30,000 homes. With files from The Associated Press