Authorities across the US are on alert as a winter storm brings freezing winds, ice and snow to many areas in southern states.

President Joe Biden has approved a state of emergency in Texas where a surge in demand for electricity has led to widespread power cuts. More than 4.3 million homes and businesses were without power.

The storm was part of a massive system that brought snow, sleet and freezing rain to the southern Plains and was spreading across the Ohio Valley and to the Northeast.

Massive power outages across Houston included a facility storing 8,000 doses of Moderna vaccines, and health officials scrambled to find takers.

By mid-morning, 3,000 flights had been canceled across the country.

The storm arrived over a three-day holiday weekend that has seen the most US air travel since the period around New Year’s.

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