As the night grew darker, a cold wind whipped across the asphalt expanse of the vintage Rubidoux Drive-In Theatre in Riverside, Calif. A howling gust banged open the door to the snack bar, where hot dogs glistened on metal spits and the black-and-white linoleum floor gleamed.

Quentin Tarantino’s “Django Unchained” flickered to life on the colossal screen – for an audience of eight cars.

This time of year is always slow at drive-in theaters, which have been struggling with declining attendance for decades. But it’s not just cold weather that has made this a winter of discontent. The digital revolution is here, and that could mean lights out for many of the nation’s 368 surviving drive-ins.

Hollywood is expected to stop distributing 35 mm film prints to all U.S. theaters later this year. The vast majority of indoor theaters – hardtops, in drive-in lingo – have already converted to digital projectors, but 90 percent of drive-ins have not, according to an industry trade group. Conversion costs of $70,000 or more per screen could be too expensive for many drive-ins.

The Rubidoux plans to convert to digital projection, but its owner says the switch will be a struggle for many others.

“There’s been panic, definitely,” Frank Huttinger said. “Ma-and-pop outfits, second- or third-generation places, are hesitant to put up all that money.”

The drive-in market today is a shell of what it was in the late 1950s, when teens and big families in big cars found drive-ins a fun alternative to indoor theaters. At their peak, there were more than 4,000 drive-ins, accounting for 25 percent of the nation’s movie screens. Today, that’s down to 1.5 percent.

By the late 1980s, more than three-quarters of American drive-ins had closed as multiplexes proliferated. Urban sprawl and soaring land values led many to be bulldozed to make way for malls and other commercial developments.

The drive-ins that survived have been doing better in the past decade, spurred partly by cost-conscious families who can see double features or first-run movies at half the price of the hardtops, said National Association of Theatre Owners spokesman Patrick Corcoran.

In most of the country, drive-ins close for the winter. Some may not reopen this spring because of the high cost of digital conversion, said John Vincent Jr., the president of the United Drive-In Theatre Owners Association. He declined to speculate on the number that may close.

“It’s a tough pill to swallow,” Vincent said. He plans to spend $75,000 to convert the drive-in he owns on Massachusetts’ Cape Cod.

More than a decade ago, Hollywood created a financing plan to help traditional indoor theaters with the digital transition. Each time a cinema shows a digital movie, the studios give them a “digital print fee” funded by the nearly $1,300 that the studios save on making and shipping a 35 mm print, said Chris McGurk, the chairman and chief executive of Cinedigm, a digital equipment provider for theaters.

But there is no such plan for drive-ins. Cinedigm and officials from the National Association of Theatre Owners said they are negotiating with the studios for a virtual print fee for drive-ins, but neither they nor studio officials could give details of the plan or say when it would be introduced.