Retailers want you to know how hard they have it this holiday shopping season.

Along with usual deals on blenders, toys and fluffy slippers, chains this year are offering crash courses about the supply chain, staffing shortages and inventory challenges they are facing in the final months of 2021. The anxiety has trickled down to shoppers, with many shopping for Christmas before Halloween or worried they should be.

“Best...

Retailers want you to know how hard they have it this holiday shopping season.

Order backlog

Along with usual deals on blenders, toys and fluffy slippers, chains this year are offering crash courses about the supply chain, staffing shortages and inventory challenges they are facing in the final months of 2021. The anxiety has trickled down to shoppers, with many shopping for Christmas before Halloween or worried they should be.

“Best time to order? Right now!” reads a banner near the top of Lands’ End home page. Its website also outlines reasons a product might not be available or delayed, including a global shipping and airfreight shortage, rail congestion and high consumer demand.

“We want to be real with you: we’re facing some unique challenges this year,” starts a five-paragraph note on L.L. Bean Inc.’s website. The retailer tells shoppers to buy products they want early because of supply-chain uncertainty, worker shortages and similar issues at the companies that supply their goods.

A customer at the L.L. Bean flagship store in Freeport, Maine. The retailer added a warning about supply-chain backups to its website, below.

Photo: Robert F. Bukaty/Associated Press

Photo: L.L. Bean

Some retailers are being more subtle. “Get a head start on holiday prep,” said the Target Corp. website Wednesday. Target started offering 2021 holiday deals in early October, weeks earlier than pre-pandemic years.

“I said, ‘OK, if I want to get what I want to get, I better get it now,’ ” said Kathy McAlpine, a retiree who lives in Monroe, Maine. After the Little Tikes toy cash register her granddaughter wanted sold out at local stores, she ordered it on Amazon.com, she said.

Ms. McAlpine said she used to wait until the weeks before Christmas to shop for gifts. Last year, after shelves emptied of toilet paper and some groceries in stores near her home, she wrapped up Christmas shopping by mid-November, the 70-year-old said. This year, she rushed to finish her holiday gift shopping this month.

“All those products are sitting out on those ships,” she said, referring to backlogs at U.S. ports of container ships delivering goods from Asia. “I just wanted to get it done so if this Covid thing took off again, I was going to make sure I had what I wanted.”

The explanations and nudges from retailers are a sign that many are worried about how supply-chain problems will affect holiday sales and customer satisfaction during the time of year when many bank a large percentage of their revenue. And there is plenty of upside for retailers to lock in sales early.

“We all went through the toilet paper crisis. It’s on everyone’s mind and covered every day, so much so that people are counting ships,” said Rod Sides, head of the retail and distribution practice at consulting firm Deloitte LLP. Retailers are pushing holiday deals earlier to grab their share of the spending, he said.

Early buying also encourages shoppers to spend more overall, a longtime phenomenon that had retailers moving holiday deals earlier each year before the pandemic accelerated the trend. Deloitte estimates that shoppers who start buying before Thanksgiving spend around 23% more than those who start after Thanksgiving.

A delivery driver sorted packages at a Deutsche Post DHL site in Cologne, Germany, this month.

Photo: Rolf Vennenbernd/dpa/ZUMA PRESS

Carol Tomé, chief executive of United Parcel Service Inc., said Tuesday on a conference call that the company was hearing from some surveys that around 50% of shoppers aim to be done with their holiday shopping by Cyber Monday, the Monday after Thanksgiving. That has led some retailers to move holiday promotions forward, she said, which led to higher-than-usual package volumes last week.

We Want to Hear From You

How are supply-chain issues having an impact on your holiday shopping? Tell us in the form below.

DarDra Coaxum, co-owner of New York restaurant group Harlem Shake, said she is watching friends fret over buying gifts this month before stores sell out. She herself has decided to opt out of Christmas gifts altogether. “I’m trying to kind of skip the season a little bit,” she said.

Shopping has become stressful during the pandemic, with out-of-stock goods or long lines, said the 33-year-old. “We had a chance to just sit with ourselves and get to know ourselves” during the pandemic, she said. “I’d really like to get away from capitalism.”

All that anxiety is likely to produce brisk holiday sales. The National Retail Federation Wednesday estimated holiday sales will rise between 8.5% and 10.5% from last year—when holiday sales also grew at many retailers—totaling roughly $843 billion to $859 billion. The estimate for retail sales in November and December was the largest ever rise predicted by the industry group. Deloitte in September forecast holiday retail sales would increase between 7% and 9% from a year ago.

A toy shelf at a Target store in Houston this week.

Photo: Brandon Bell/Getty Images

“This is the first time I’ve actually done holiday shopping in October,” said David Acharya, a 48-year-old private-equity investor who watched with alarm as his local stores carried fewer items. He knew cargo ships were piled up at ports and industrial-production data showed signs of slowing, he said. “I saw all this and said, ‘This will definitely affect Christmas.’ ”

“If there is one person in the family that would look ridiculous not having enough gifts, it’s the uncle who is the private-equity executive,” said Mr. Acharya. He said he already purchased magnetic building tiles for a niece and other toys, but is still hunting for larger electronics that have been hard to track down.

Even retail executives are getting their shopping done early. Bjørn Gulden, the chief executive of German sportswear company Puma SE, said he expects delivery delays to stretch into early next year. Covid-19 lockdown measures in Vietnam, where Puma sources around a third of its goods, port congestion in the U.S. and a lack of shipping capacity globally have all played a role in the delays, Mr. Gulden said.

“As I said to my wife, if you want to buy Christmas presents, you should buy now,” Mr. Gulden told reporters after the company released its third-quarter results on Wednesday. “It’s not a joke. I think there will be racks in retail that are more empty than you would like when you go Christmas shopping just because of the general situation.”

—Georgi Kantchev contributed to this article.

Write to Sarah Nassauer at sarah.nassauer@wsj.com