Shoppers like to complain that holiday decorations appear earlier and earlier. This year, so are the job ads.

The holiday hiring binge is accelerating for retailers such as Target Corp. and Macy’s Inc., which add thousands of workers to process surging online orders. E-commerce sites double or even quadruple their warehouse staff. Online giant Amazon.com Inc. adds to the hiring frenzy, as do logistics companies and package-delivery services such as United Parcel Service Inc. and FedEx Corp. Some firms posted their first holiday...