A powerful storm hit the western United States on Wednesday, leaving two people dead and half a million customers without power, according to local authorities.

The storm, which began on Tuesday night and lasted into Wednesday, caused winds of up to 90 miles per hour (145 kilometres per hour), disrupted air travel and downed trees on roads, the National Weather Service said.

The Washington State Fire Department said a woman in her 50s was killed on Tuesday night after a tree fell on a homeless shelter in the city of Lynnwood. In a similar incident in Bellevue, east of Seattle, another woman died after a tree fell on her home.