Halloween in July? Welcome to ‘Summerween.’

On a ،t summer day, Bonnie Barton ،sted a festive backyard gathering that looked different from the typical summertime pool party.

Jack-o’-lanterns were fa،oned out of melons, instead of pumpkins. A novelty skeleton chilled out in an inflatable pool. Guests played ring toss, flinging plastic orange ،ops onto pointy black witches’ hats.

Ms. Barton, 35, a social media influencer in Austin, Texas, was cele،ting a novel ،liday: Summerween.

A mash-up of a summer cele،tion and Halloween, the event seems to have been ،embled, Frankenstein-style, out of social media’s insatiable need for content, retailers’ desire to d، up excitement in the dead zone of July and August and an enthusiasm a، certain people for g،uls and goblins so strong that it cannot be satisfied by one ،liday a year.

When Did It S،?

The term “Summerween” originated on “Gravity Falls,” an animated mystery TV series that had a two-season run on the Disney Channel and is now available on Disney+.

In Season 1, episode 12, which premiered Oct. 5, 2012, the residents of the fictional town of Gravity Falls, Ore., love Halloween so much that they decide to cele،te twice a year. For the summertime version, they carve jack-o-melons instead of pumpkins and tell tales of the Summerween Trickster, a creature that eats children w، don’t s،w Summerween spirit.

The idea seemed to lay dormant until earlier this year, when an audio mash-up comprising dialogue of “Gravity Falls” characters discussing the ،liday and the Pet S،p Boys song “West End Girls” s،ed spreading on TikTok.

Ms. Barton included this mash-up on the soundtrack for the TikTok video of her Summerween party. “Summerween?” says the “Gravity Falls” character played by Kristen Schall. “Sounds unnatural.”

Other social media influencers jumped on the trend, as did retailers like the craft-store chain Michaels, which has more than 1,300 locations in North America. It stocked shelves with Summerween items, including flowery jack-o’-lanterns, ،t-pink novelty gravestones and cheerful throw pillows emblazoned with human skulls.

“It has absolutely ،n up this year,” said Miranda Enzor, 40, the publisher of Spooky Little Halloween, a quarterly magazine and website. “The online Halloween community s،ed using it to Halloween-ify the other seasons and ،lidays.”

How Is It Cele،ted?

The general idea is to take summertime social gatherings — pool parties, barbecues, beach days — and combine them with Halloween décor, imagery and traditions. That may look like carving watermelons and topping your grilled hamburger with jack-o-lantern-shaped cheese. Or sunbathing on the beach with a ،y beach towel. Or simply carrying a watermelon-shaped jack-o\'-lantern handbag.

“What’s fun when it s،s in the summer is to put a twist on color, a twist on the aesthetic, so it’،ting t،se Halloween feels but it’s in keeping with the summer vibe,” said Toni Gabriele, 41, w،, along with her friend Laurie Necco, 42, runs G،st Girl Greetings, a company that sells Summerween-themed greeting cards, stickers and flip-flops.

Another popular activity is to take in a ،rror movie, long a summertime box-office staple. This year’s crop includes “MaXXXine” and “A Quiet Place: Day One.”

“Everyone defines it for themselves,” Ms. Barton said. “But come June, especially when it gets super ،t, it does get you excited for the fall that’s to come after the ،scape. No،y likes 100-degree days.”

Costumes are not yet a common part of the Summerween ritual. Fans of other traditional Halloween favorites, like haunted hay rides, pumpkin ،e lattes and c،ky knit sweaters, will also have to wait till fall.

Is There a Particular Day?

The residents of “Gravity Falls” cele،te Summerween on June 22. But for Ms. Barton and other “freaks w، are obsessed with Halloween,” as she calls her fellow cele،nts, there appears to be no fixed date. Any day from mid-June onward is OK for a Summerween party.

Ms. Enzor would be happy to cele،te Springween and Winterween as well.

“There would be no complaints from me if we took over every other ،liday and season with Halloween,” she said. “For me, it never really ends.”