[UPDATE: Organizers say the festivities will start at 4 p.m. instead of noon on Sunday due to weather.]

Science fiction fans have been braving the snow-pocalyptic weather this week for a reunion of sorts at the Boston Sci-Fi Film Festival, which is celebrating its 40th anniversary this year. The 10 days of movie screenings starring aliens, robots and zombies peak Sunday with a 24-hour marathon. I trudged over to the Somerville Theatre to learn more about the fest’s history and cult appeal.

Paul Rubin of Lexington has been coming to Boston's Sci-Fi Festival for 30 to 35 years. (Courtesy)

Hardcore followers of science fiction know full-well that they're a unique breed, so when the opportunity arises to bond over popcorn with like-minded people, they jump at the chance. Take devout attendee Paul Rubin of Lexington who struggled to pin down exactly how long he’s been coming to the Sci-Fi Festival and “thon,” as it’s known.

“Somewhere between 30 and 35 years,” he estimated, laughing, “I‘ve lost track. I know I missed number 10…and I think I started at number six…I'm not quite sure, might have been number five. I might’ve missed one or two others when I had small kids.”

Like a lot of fans, this 68-year-old’s affection for sci-fi started with books and TV when he was a kid.

“Channel 68 – this was years ago, before cable – used to do Creature Double Feature,” he recalled.

For those not familiar with that syndicated weekend horror broadcast, it aired all-manner of creepy, spaced-out, even schlocky movies made between the 1930s and 1970s, including those featuring everyone’s favorite giant, fire-breathing monster, Godzilla.

“And I was a big fan of the 'Twilight Zone' and 'Science Fiction Theatre',” Rubin continued, “which was George McFly's favorite TV show.”

Spoken like a true movie lover. In case you don’t remember, McFly was the uber-nerdy hero in “Back to the Future” who wrote science fiction stories about visitors coming down from other planets.

Hundreds of visitors from this planet usually show up for the 24-hour marathon – or "thon," as it's affectionately called. Fest organizer Garen Daly acknowledges this winter's horrific weather, but has faith that his brethren will not miss tomorrow's big event. He even sent out a fun, Star Wars-inspired graphic to pass holders that reads, "Damn The Snow! The Thon Strikes Back."

A card sent out from the festival organizers. (Boston Science Fiction Film Festival)

“Every year around this time, when it is miserable New England weather and it’s snowing like a (pause) whatever outside, we have this wonderful community that arises,” Daly mused, “And then when it ends it fades off into the snow, only to arrive a year later.”

The festival’s origins can be traced back 40 years to Orson Welles Cinema in Cambridge, which burned in 1986. After the devastating fire, Daly, who managed the art house, took over the programming.

The Orson Welles Cinema in 1978 where the sci-fi festival was born. (Bruce Bartoo)

It all started as a horror and sci-fi fest, then morphed into a marathon, and now it’s both. Fantastic creatures have slithered across screens at cinemas in West Newton, Coolidge Corner, Dedham and Somerville, where it’s been for the past 10 years or so. The projectionists there (and at those other theaters) have traditionally prided themselves on being meticulous about showing celluloid films as they’re meant to be seen. And Daly says he’s willing to bet Boston's is the oldest genre-specific festival in the U.S.

“I've been in the business for about 45 years, and I have yet to see another film festival like us that's this old. So, until someone proves me differently, we're the oldest in the country,” he said, smiling.

For Daly this genre-specific festival and it's 24-hour marathon are pre-cable, pre-Netflix examples of "original binge viewing." The line-up is always a diverse mix of brand new films and classic sci-fi including titles such as Stanley Kubrick’s iconic “2001: A Space Odyssey.”

Science fiction is clearly popular these days – what with aliens, zombies and the apocalypse being all the rage. But Daly admitted there have been challenging moments. Even so, he’s remained loyal to the cause, and said he keeps it going for the community that returns year after year.

“They're amazing,” he gushed. “There is a certain amount of trust I have in them and they have in me, and I like that. Although there's been some tough times, never have I thought about giving it up.”

Festival producer Garen Daly is making sure the shows go on throughout the snowstorm. (Harry O. Lohr, Jr.)

In fact, Daly is looking to expand the Sci-Fi Film Fest in the future. That's music to die-hard passholder Paul Rubin's ears because, he said, this fest plays an essential role in preserving old-school sci-fi culture and aesthetics.

“Especially now, where there's so much digital media, and a lot of Hollywood-ization of science fiction films, I think it's really important to keep a lot of the classics going,” he said. “And it's an opportunity to see them on the big screen…with 500 of my best friends!”

Festival producer Daly will be ready for the undaunted ones who make their way across the frozen, Hoth-like tundra to the Somerville Theatre with their tooth brushes and sleeping bags in tow.