Two powerful cyclones smashed into northern Australia, knocking out power to thousands, tearing roofs off houses and prompting coastal residents to flee their homes.

The twin storms, dubbed the "cyclone sandwich" by locals, struck within hours of each other, 1,500 miles apart, amid warnings the violent winds and drenching rains could prove deadly..

Cyclone Lam hit a sparsely populated stretch of the Northern Territory, while the more powerful and potentially dangerous Cyclone Marcia crossed over small towns along the east coast of Queensland state, packing wind gusts up to 180mph.

"Over the next few hours, many thousands of Queenslanders are going to go through a harrowing and terrifying experience," Queensland premier Annastacia Palaszczuk said.

"This is a severe cyclone. I want everyone to take all the precautions that they possibly can take."

About 30,000 people living in and around the Queensland town of Yeppoon - 400 miles north of the state capital Brisbane - were originally expected to experience the worst of the storm.

More than 100 schools were closed and nearly 900 residents in low-lying areas were told to evacuate their homes. But a slight change in the cyclone's path spared the town the most ferocious winds.

Yeppoon resident John McGrath, who was riding out the storm with his family in their house just 100 yards from the beach, watched as the roof of his neighbour's home peeled off, flew through the air and landed across the road.

The walls of his own house were rattling, water was beginning to seep through his windows and the ocean's swells were growing enormous.

"I'm getting nervous," he said by telephone over the roar of the storm's winds. "As long as our roof holds together, I think we'll be OK."

Mr McGrath, his wife and their two children, Emma, six, and Michael, four, dragged cushions and mattresses into a bathroom at the back of the house and were planning to stay there until the cyclone subsided.

"We're going to have lots of wet things and our town's going to be a mess," he said. "It escalated so rapidly, it was crazy."

Officials pleaded with hardened Queensland residents - no strangers to violent cyclones - to take the storm seriously. A cyclone of similar strength, Yasi, hit the state in 2011, destroying scores of homes but causing no deaths.

"This is going to be a calamity, there's absolutely no doubt about that," Queensland police commissioner Ian Stewart said.

The storm was weakening as it headed south toward the city of Rockhampton, home to about 80,000 people. Ms Palaszczuk warned residents to stay inside and brace for the impact.

More than 30,000 Queensland homes were without power, and some houses had lost roofs and doors.

In the Northern Territory, Cyclone Lam struck a remote stretch of coast, tearing up trees and downing power lines, but causing no major damage as it weakened and moved inland. No injuries were reported.