Superstorm Sandy drove the number of people seeking unemployment benefits up to a seasonally adjusted 439,000 last week, the highest level in 18 months.
The Labor Department says applications increased by 78,000 because a large number of applications were filed in states damaged by the storm. People can claim unemployment benefits if their workplaces close and they don't get paid.
The storm may distort claims for another two weeks, the department has said.
The four-week average of applications, a less volatile number, increased to 383,750.
Before the storm, applications fluctuated between 360,000 and 390,000 this year. At the same time, employers added an average of nearly 157,000 jobs a month. That's barely enough to lower the unemployment rate, which was 7.9 percent in October.