Australia and US counting cost of battering by extreme weather

Officials had issued days of increasingly dire warnings, and said lives were spared because people followed instructions to flee to evacuation centres or bunker themselves at home in dozens of cities and towns in Cyclone Yasi's path on the north east coast.

Hundreds of houses were destroyed or seriously damaged, and the homes of thousands more people are barely liveable.

The storm was as powerful as forecasters predicted – ferocious winds up to 170mph at the core, flood-inducing rain and tidal surges that sent waves crashing ashore two blocks into seaside towns. Several small towns directly under Yasi's eye were devastated, hundreds of millions of dollars of banana and sugar cane crops smashed and power to more than 180,000 homes severed.

Yasi crossed the coast around midnight at the most-destructive category five rating, and the swirling storm pattern immediately began weakening once it was over land. It was still strong enough to hold a category one cyclone rating 500 miles inland late on Thursday where it was threatening to cause flooding in the Outback town of Mount Isa.

The disaster zone was north of Australia's worst flooding in decades and is sure to add substantially to the estimated 3.5bn cost of the damage since late November. The government has already announced a special tax nationwide to help pay for the earlier flooding.

Queensland premier Anna Bligh said several thousand people would be temporarily homeless and Red Cross Australia and local governments were working on registering people in need and finding places to house them.

Emergency services minister Neil Roberts said initial assessments were that more than 280 houses were damaged in the three hardest-hit towns, and crews could not reach at least four others, so the tally would rise.

Severe weather in the US, meantime, has killed at least 12 people as nearly half the country is smothered in a shroud of white. Chicago's 20in of snow was the city's third-largest on record.

Tens of millions of people have heeded official warnings and are staying at home. A storm that produces 20in of snow is said to be a once in every 50 years event.

Although skies were beginning to clear by mid-afternoon, the storm promised to leave a blast of bitter cold in its wake. Overnight temperatures in northern parts of the Midwest were expected to fall as low as minus 30C, with wind chills dropping to minus 35C.