Think of your summer leisure time -- beaches, baseball, barbecues, vacations, camping, fairs, fireworks, sunshine... What can the TV programmers offer to pull you away from all that?

How about monsters, murders, alien invaders, serial killers, horror, gore, and violence?

Seems counterintuitive, right? And yet, that's what this summer's TV fare looks like, a parade of grimness and bleakness at a time when people are most likely to seek escapism.

This year's summer of darkness began with the launch on Fox last month of "Wayward Pines," the new series based on Blake Crouch''s novels and featuring the signature spooky touch of "Sixth Sense" and "Signs" director M. Night Shyamalan. So far, the show's highlights have included vehicular mayhem, cultish creepiness, mysterious conspiracies, summary executions, and hints of lurking monsters.

Not to be outdone, NBC has "Aquarius," with David Duchovny putting on his Fox "Creepy" Mulder hat as a 1960s sleuth who crosses paths with a Charles Manson who has yet to descend completely into madness and multiple murders. (Notice how, whenever they make a show or movie about the 1960s that's not "The Wonder Years," it's never about peace and love and music and civil rights victories, it's always about war and social unrest and drugs and hippie excesses?)

And over on ABC, they have "The Whispers," based loosely on Ray Bradbury's story "Zero Hour," a drama series in which an alien presence persuades children to try to kill their parents. The pilot, which aired on Monday, was co-directed by Mark Romanek, the filmmaker behind such art-house chillers as "One Hour Photo" and "Never Let Me Go."

Even on the supposedly benign ABC Family channel, there's the new "Stitchers," about a woman who helps solve murders by mind-melding with the dead victims. Apparently, conspiracy drama "Pretty Little Liars" (which started as a summer series on the channel) didn't bring enough darkness to a channel otherwise known for "Gilmore Girls" reruns and Harry Potter marathons.

Coming soon: SyFy's "Dark Matter" (June 12), about a group of suspicious amnesiacs aboard a lost spaceship and "Killjoys " (June 19); a gritty drama from the producers of "Orphan Black" about interstellar bounty hunters; AMC's "The Making of the Mob: New York" (June 15), a documentary series about the violent history of organized crime in America, and "Humans" (June 28); a "Blade Runner"-like sci-fi series about a society too dependent on replicant servants; TNT's "Proof" (June 16), starring Jennifer Beals as a surgeon and grieving mom who searches for evidence of life after death; USA's "Complications," (June 18), another show about a doctor who's also a grieving parent; Sundance's "Deutschland 83 (June 17); a Cold War undercover spy drama that sounds like a West German version of "The Americans"; MTV's "Scream" (June 30), based on the old slasher-movie franchise; and CBS's "Zoo" (June 30), based on the James Patterson tale about a worldwide pandemic of animal attacks on humans. Even HBO's new comedy "The Brink" (June 21) is a "Dr. Strangelove"-like satire about well-placed diplomats and servicemen trying to prevent World War III. And those are just the new series debuting in June.

When did sunny-season TV get so dark? Part of the answer has to do with the changing nature of summer TV -- a season that didn't even exist 25 years ago, back when there were only four broadcast networks that followed a decades-old tradition of airing new programming from September to May and reruns during the warm-weather months when no one seemed to be watching. That all changed in the early 1990s, with the summer success of CBS's gentle dramedy "Northern Exposure" and Fox's sunny-California teen soap "Beverly Hills, 90210." From then on, summer seemed to be an ideal time to launch low-key escapist fare. When the reality boom hit in the early 2000s, summer saw the successful launches of CBS's "Survivor" and "Big Brother" and Fox's "American Idol."

But the success of these summer series made TV programmers realize that the old September-to-May schedule was an anachronism. If there was no longer a time when viewers didn't hunger for new programming, then you could launch a new series at any time of year. So there was an increased demand for new programming of all kinds, not just breezy comedies, light dramas, and fun reality competition series.

In recent summers, in addition to "Pretty Little Liars," we've seen such series as HBO's gory and apocalyptic vampire drama "True Blood" (a summer show for all but the first of its seven seasons), FX's envelope-pushing comedy "Louie" (known for its dark and intense exploration of topics TV would usually rather avoid), and AMC's "Mad Men" (which premiered in July, 2007) and "Breaking Bad" (which didn't take off until it became a summer series in its fourth season, in 2011). On the networks, CBS has offered Stephen King adaptation "Under the Dome" and chilling sci-fi drama "Extant," both of which are returning this summer.

Even so, why are we watching these shows when we could be frolicking outside? It could be that years of acclaimed antihero dramas on both cable and network TV have primed us to accept brooding, intense dramas and darkly satirical comedies year-round. (Exhibit A: AMC's "Halt and Catch Fire," which looks at the dawn of the personal computer industry through the psychodramas of the tortured souls whose demons helped drive their innovations. Despite modest ratings, the series -- and its enigmatic, charismatic Don Draper-like protagonist, played by Lee PaceI -- returned for a second season on Sunday.) It could be that we're so accustomed to violent and spooky fare, from "Hannibal" to "The Walking Dead," from "American Horror Story" to "Game of Thrones," that our hunger for such shows does not diminish during the summer. Have the networks, which have all but abandoned comedy for the upcoming fall season, decided that it's too hard to figure out how to make viewers laugh in these sensitive times? Or could it be that our own lives are so dramatic and stressful, that the world brought to us by the news is so chaotic and ominous, that even shows this horrific seem to us like cathartic escapism?

Whatever the reason, we're going to be stuck with this gloom and doom on TV until fall, when we'll get... more of the same. Oh, well. At least we can turn to such light and fluffy entertainment as the new seasons of "Orange Is the New Black" and "True Detective." Oh, wait...