Retailers are ramping up hiring for the holiday season, but fewer seasonal employees are expected to be taken on this year to help customers in stores and assemble online orders in warehouses.

E-commerce giant Amazon said Thursday it will hire 250,000 full, part-time and seasonal workers, including 4,000 in Massachusetts, for the crucial shopping period, rounding out a series of announcements made in recent weeks by the country’s top retailers.

Target said in September it planned to bring in roughly 100,000 seasonal employees and offer current employees the option to work extra hours during the holiday shopping period.

Meanwhile, the department store Kohl’s encouraged people to apply for positions but stayed mum on its plans, mirroring Walmart, which said it’s been hiring store associates throughout the year.

The holiday shopping period is the busiest time of year for both online and brick-and-mortar retailers.

The consulting firm Deloitte forecasts U.S. retail sales will increase 2.3% to 3.3% between November and January and reach a total of $1.59 trillion. EY-Parthenon, the consulting arm of Ernst & Young, forecasts a similar 3% jump in sales during the traditional November-December period.

Online sales, a growing segment of retail, is expected to increase 8.4% and reach a record $240.8 billion, according to Adobe, which tracks e-commerce transactions.

Amid the growth in online shopping, the delivery giant UPS said it planned to hire 125,000 seasonal workers for the holiday rush, up from 100,000 last year.

“At the moment, retailers appear optimistic for a strong holiday shopping season, which is being reflected in the hiring plans of major retailers and warehouses,” said Andy Challenger, senior vice president at the outplacement firm Challenger, Gray & Christmas.