Network TV traditionally treats itself to a summer break, choking the airwaves with reruns and mind-numbing reality shows, while executives do their best to stay out of the sun so as not to reveal themselves as blood-sucking vampires.

So why is “Under the Dome,” a $40 million-plus project from some guys named Stephen King and Steven Spielberg, premiering Monday on CBS? Because TV no longer can afford to take a vacation.

“It’s truly a reflection of the fact that summer isn’t a wasted time period anymore,” said Noah Eve­rist of Compass Point Media, a Minneapolis-based consulting firm. “We can thank cable for that.”

The theory that Americans are too active to stay indoors when the weather turns warm was dashed by the success of such shows as TV Land’s “Hot in Cleveland,” Lifetime’s “Army Wives” and FX’s “Louie,” all of which aired initially in June.

Turns out lounging in front of the TV screen is a year-round activity.

CBS is also testing the new summer model with “Unforgettable,” a Poppy Montgomery drama that was canceled but is being brought back for a limited run starting July 28. On Sunday, NBC is premiering a new crime drama, “Crossing Lines,” starring Donald Sutherland. ABC is fooling around with the soapy series “Mistresses.”

“Under the Dome,” based on a King novel so massive that Arnold Schwarzenegger could use copies of it in the weight room, may be the prototype for future programming. The story tracks the fate of residents in a small town who suddenly find themselves isolated from the rest of the world and react like they’ve never read “Lord of the Flies.” Aliens will also pay a visit.

It’s a highly serialized, dense 13-part series filled with the kind of gruesome twists and turns we’re used to seeing on cable.

In fact, “Dome” was originally developed for Showtime. When the pay-cable network eventually passed, CBS Entertainment president Nina Tassler pounced. Both CBS and Showtime are owned by Viacom.

“Nina wanted to do shorter, serialized series in the summer that viewers could sink their teeth into,” said Neal Baer, showrunner for “Under the Dome,” speaking by phone last week from North Carolina, where he was in the process of shooting the 10th episode. “We believe that people are hungry for something new in the summer.”

“New” doesn’t mean cheap. Networks have to charge lower ad rates in June, July and August because their viewership has traditionally dropped by as much as one-third.

To defray the cost of the series — budgeted at more than $3 million an episode, which is high for a network show — CBS teamed up with, which will make episodes available four days after they’re broadcast. Amazon Prime members will be able to stream the series as part of their subscription package, while others can pay to download episodes.

Executives are also hedging their bets by presenting “Dome” as a limited series that ends in August. That should appease people who are tired of getting hooked on dramas, only to kick over their coffee table when shows are canceled before reaching a proper conclusion.

That doesn’t mean there couldn’t be more “Dome” next summer. If ratings are solid, the show will return next year with a brand-new story line, Baer said. It’s a model that has worked well in Europe as well as for cable shows such as “American Horror Story.”

“Limited series are going to be a part of network programming, at least in the near future,” said media consultant Everist. “They give them a chance to test material.”

They also give producers a little more room to breathe.

Baer has built his career working on long-running shows like “ER” and “Law & Order: Special Victims Unit,” each of which demanded at least 22 episodes a season. That’s fine for a procedural, Baer said, but for a serialized series it’s agony for both the creative team and the audience.

With just 13 episodes, the network can schedule a three-month run without interruptions. It also affords Baer a little more time to nurture the show.

“I like it,” he said. “It’s a little more manageable to have a life.”