Applications increased by 15,000 to a seasonally adjusted 382,000, the Labor Department said Thursday. That's up from 367,000 the previous week. The four-week average, a less volatile measure, increased for the fourth straight week to 375,000.
Isaac made landfall as Category 1 hurricane on Aug. 28 in southeastern Louisiana and was later downgraded to a tropical storm. It disrupted work in nine states and boosted applications by roughly 9,000, Labor officials said.
Applications for unemployment benefits reflect the pace of layoffs.
The data on unemployment applications follow last week's disappointing August employment report. And it comes as the Federal Reserve concludes a two-day meeting. Many analysts expect the Fed will announce new steps to boost the economy when the meeting ends.
Jim O'Sullivan, chief U.S. economist at High Frequency Economics, said that after excluding the impact of the hurricane, applications are likely closer to 370,000. Still, the job market has shown little vigour this year.
"While today's reading was likely exaggerated, and we do not believe the labour market is weakening, the trend has been and still is weak enough to trigger more Fed easing today," O'Sullivan said.
Employers added only 96,000 jobs in August, below July's gain of 141,000 and far below the average 226,000 a month added in the January-March quarter.
The unemployment rate dropped to 8.1 per cent from 8.3 per cent, but only because the number of people working or looking for work fell.
The total number of people receiving unemployment aid fell to 5.4 million in the week ending August 25, the latest data available. That's about 80,000 fewer than the previous week. Some of the decline may result from more people getting jobs. But many recipients are using up all the benefits available to them.
Many economists have noted that while layoffs are falling, overall hiring isn't picking up at the same pace. A separate monthly report from the Labor Department this week showed that layoffs were at the lowest level in July in the 11 years the government has tracked the data.
The economy isn't growing fast enough to support much more hiring. It grew at a tepid 1.7 per cent annual rate in the April-June quarter, down from 2 per cent in the January-March quarter and 4.1 per cent in the final three months of last year.
Growth isn't likely to get much better for the rest of this year. Economists expect it to grow at a roughly 2 per cent pace. That's typically too weak to create enough jobs to lower the unemployment rate.
High unemployment and sluggish growth has prompted many economists to forecast that the Federal Reserve will announce new steps to boost the economy after its two-day meeting ends Thursday. Those steps could include a third round of Treasury bond purchases. The goal of the purchases would be to lower interest rates and spur more borrowing and spending.
Fed Chairman Ben Bernanke said in a recent speech that weak hiring is "a grave concern" that causes "enormous suffering."