Last week’s devastating windstorms in the central and south-eastern United States are the first sign that this northern summer is going to be a bad one. Forecasters say up to 11 tropical storms and nine hurricanes could threaten the country’s eastern seaboard between now and November.

The emerging La Nina weather effect, which brings greater rain volumes to Australia, also ensures more frequent and bigger storms in the US.

Damage of more than $11 billion was caused by storms in the US during the past two years, although last week’s cost $1.2 billion.

The Insurance Information Institute said homeowner insurance rates may rise in some cities, especially in the increasingly populous coastal areas and in inland areas that are particularly prone to tornadoes.