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(CNN) — Weary retailers continue to battle pandemic uncertainty as the Delta variant causes new spikes in coronavirus infections. But for now, at least, expectations for a merry holiday season remain intact.

What’s happening: Data published Thursday is expected to confirm that US retail sales declined for the second straight month in August.

But new forecasts from Deloitte, Bain & Company, and Mastercard predict a huge sales boom in the coming months, the most important time of the year for retailers.

Deloitte estimates that holiday sales will increase between 7% and 9% in 2021 as vaccinations help shoppers feel more comfortable venturing out to spend some of the cash they’ve been hoarding.

“A steady decline in the savings rate to pre-pandemic levels will support consumer spending and keep retail sales elevated this season,” said Daniel Bachman, Deloitte’s US economic forecaster. “Further, e-commerce sales will continue to grow as consumers demonstrate an ongoing and steady movement toward buying online across all categories.”

The consulting firm expects online sales to jump between 11% and 15% year-over-year, reaching up to $218 billion.

Mastercard, for its part, sees US retail sales rising 7.4%. While online shopping could rally 7.6%, in-store shopping is expected to increase by 6.6% compared to 2020. Bain & Company is also calling for a 7% sales growth rate in November and December.

“The pandemic has impacted nearly every inch of the retail industry,” said Aaron Cheris, the head of Bain & Company’s Americas Retail practice. “However, heading into this holiday season, we also see important tailwinds for nominal retail growth, including boosts from inflation, rebounding employment, healthy savings rates and wage growth.”

But wait: Supply chains remain badly tangled, causing shipping costs to soar. Some companies worry that empty shelves and shortages of in-demand products could dampen the mood.

“The demand is going to be there,” MGA Entertainment CEO Isaac Larian told CNN Business late last month. “What is not going to be there is the product to fill the demand.”

Mastercard thinks retailers will try to get around supply chain concerns, as well as persistent difficulties in hiring workers, by offering earlier holiday promotions in stores and online — particularly for electronics and clothing items.

“This holiday season will be defined by early shopping,” Steve Sadove, senior advisor for Mastercard, said in a statement.