AYR, Australia — Torrential rain hampered relief efforts on Thursday after a powerful cyclone wreaked havoc in northeast Australia, with floods sparking emergency rescues as fed-up tourists wait to be evacuated from resort islands.

Cyclone Debbie has pummelled Queensland state since crashing ashore as category four storm on Tuesday between Bowen and Airlie Beach, ripping up trees, washing boats onto land and causing widespread damage.

It has been downgraded to a tropical low as it tracks southeast, but continues to pack damaging wind gusts and dump huge amounts of rain, with

Brisbane now in the firing line.

Meteorologists forecast the city would be soaked by a month’s worth of rain in a single day, with the popular Sunshine Coast and Gold Coast areas also in for a drenching before the system moves offshore on Friday.

"We have a very, very large state here and this is a very, very big weather system that’s going to wreak havoc all the way down the coast," Queensland Premier Annastacia Palaszczuk said.

Emergency service crews rescued dozens of people overnight and early on Thursday from floodwaters west of Mackay, with some plucked from roofs and tops of cars.

"Significant rainfall in Mackay -- sudden increase in calls for service. A number of rescues undertaken and still being undertaken," Queensland police tweeted.

Despite this, no deaths have been reported with only one significant injury - a man crushed by a collapsing wall. Before the cyclone hit, thousands of people moved to higher ground, out of the area or to safe refuges.

The wild weather has made the clean-up difficult as crews battle horrendous conditions to reach isolated communities and restore power. Many roads remain flooded and towns cut off with hundreds of schools closed.

A significant experience

Great Barrier Reef islands were among the worst hit.

Tourists and residents have been stranded for days on devastated Hamilton and Daydream islands, battered by terrifying winds of more than 260kmh at the height of the tempest.

They were due to be evacuated on Thursday by plane or ferry after struggling with no power and toilets not flushing as water ran low.

"They’ve been through a significant experience, but they are safe. That’s the main thing," Queensland Fire and Emergency Services Deputy Commissioner Mark Roche told reporters.

Jacqui McCullagh, who was staying on Hamilton Island, said the once-lush area was in a bad way.

"Boats washed ashore, houses without roofs, windows smashed in, trees snapped in half, gum trees torn out of the ground and those that do remain standing, are bare and lifeless," she told the local Whitsunday Times.

The military has mobilised 1,300 soldiers to help assess the full extent of damage and help the clean-up, with helicopters and planes deploying to restore infrastructure and supply emergency food, water and fuel.

Debbie has officially been declared a catastrophe by the Insurance Council of Australia, allowing claims from the disaster to be prioritised.

The economic cost to a region that relies heavily on farming is expected to be huge, with sugarcane crops hit hard and the cattle industry also impacted, officials said.

"Producers in the Whitsunday area were planting winter vegetables and they’re expected to suffer heavy crop losses as well as infrastructure, crop and irrigation equipment damage," said Queensland’s Rural Economic Development Minister Bill Byrne.

"In the Mackay district, it’s understood that the cane fields at Proserpine, Mackay and Sarina have been flattened." — AFP