If you want to get all boring and technical about it, summer doesn’t really start until late June. But as usual, Hollywood cannot be expected to adhere to basic rules of earth science. The onslaught of summer releases began in earnest Friday with “Van Helsing,” the overpriced mash of classic monsters and slick CGI effects, and won’t slow down until, well, the fall movie season prematurely gets under way in September.

Also as usual, summer is a safe haven for anyone fearing too much change or originality. “Van Helsing” may not be a sequel or remake, but it does trot out classic characters, including Dracula, Frankenstein and the Wolf Man.

The same can be said of “Troy,” in which Brad Pitt steps into the heels of Achilles. The battle epic from “Perfect Storm” director Wolfgang Petersen ended up costing $200 million, so all involved must be hoping it’s just epic enough to launch more than a thousand moviegoers into theaters. (Good or bad, though, “Troy” does have the distinction of being the only summer movie for which Homer gets a screenwriting credit.)

“The Day After Tomorrow” also hearkens back to familiar territory, fetishizing worldwide disaster (weren’t we supposed to be done with that after Sept. 11?). Roland (“Independence Day”) Emmerich is aiming to make this tale of a new ice age, starring multigenerational eye candy Dennis Quaid and Jake Gyllenhaal, just disastrous enough.

Halle Berry suits up for “Catwoman,” which mysteriously has nothing to do with either Batman or Gotham City. But really, just look at the first six words of that sentence and you know everything you need to know.

Then, of course, there is the parade of sequels. “Shrek 2” kicks off the season, and if unprecedented $10 million salaries for voice stars Mike Myers, Cameron Diaz and Eddie Murphy are any indication, it should be a very happy return. Tobey Maguire slips back into the spandex for “Spider-Man 2”; his foe this time around is the partial octopus known as Doctor Octavius. Harry Potter comes of age with “The Prisoner of Azkaban,” which should be interesting to more than just the target audience due to its unlikely director, Alfonso Cuaron, whose last movie was the decidedly non-family-friendly “Y Tu Mama Tambien.”

Anne Hathaway hopes to reclaim that Cinderella magic with “The Princess Diaries 2: Royal Engagement”; Ethan Hawke will seek to remind us of a day when he had some appealing indie cred with “Before Sunset,” Richard Linklater’s sequel to “Before Sunrise”; and Matt Damon will try to make “The Bourne Supremacy” more of a box-office hit than was “The Bourne Identity.”

In the horror milieu, “Alien vs. Predator” takes a page from last summer’s “Freddy vs. Jason.” The lusty snake is back, although sadly crazy-eyed Jon Voight is not, in “Anacondas: The Hunt for the Blood Orchid.” And Stellan Skarsgard takes a vacation from “Dogville” to frolic with Satan in “Exorcist: The Beginning.”

But really, why bother with sequels or prequels when you can just remake an existing film? That’s the tack taken by “The Stepford Wives,” which, judging by the trailers, ups the camp value of the 1975 original and also throws in Nicole Kidman as a wife wondering why all her new neighbors are so scarily perfect. “The Manchurian Candidate” updates the 1962 classic, using the Gulf War as a backdrop, and teams up powerhouses Denzel Washington and Meryl Streep. And in the fine tradition of Americanizing foreign favorites, Jennifer Lopez tries to scrub away the enduring taint of Bennifer with “Shall We Dance?,” a remake of a Japanese comedy about a businessman (here played by Richard Gere) who is rejuvenated by ballroom dancing.

You’re also allowed to laugh this summer – we hope. Will Ferrell used his newfound clout after the successes of “Old School” and “Elf” to get “Anchorman: The Legend of Ron Burgundy” rolling; Ferrell wrote the script in 2001 with former “Saturday Night Live” colleague Adam McKay. Marlon and Shawn Wayans go undercover as Hilton-esque blond girls in “White Chicks” (which, judging by the production stills, might actually be a horror movie). Snoop Dogg gets high in the sky in “Soul Plane.” And Kate Hudson continues to flout her “Almost Famous” pedigree with “Raising Helen,” which had better be a lot more charming than its woeful trailers indicate if Hudson ever wants a modicum of respect again.

Amid all the enormous budgets and rehashed stories are a few intriguing candidates for quality summertime product. Zach Braff, star of one of the best (and most underwatched) sitcoms on TV, “Scrubs,” wrote and directed “Garden State,” which was warmly received at Sundance and also features Natalie Portman and Method Man. Another festival hit, “We Don’t Live Here Anymore,” stars Mark Ruffalo and Naomi Watts as supremely unhappily marrieds. Ruffalo is also featured in “Collateral,” a drama from “The Insider” director Michael Mann, and so is some guy named Tom Cruise.

M. Night Shyamalan (“The Sixth Sense,” “Signs”) goes into the woods for his latest batch of discursive scares with “The Village,” which takes place in the 19th century and boasts A-list talents Joaquin Phoenix, Adrien Brody and Sigourney Weaver.

On the cheaper and less complicated end of the scary-movie spectrum is “Open Water,” which is said to be like “The Blair Witch Project” melded with “Jaws.” Based on a true event, it’s the terrifying tale of two divers abandoned by a tour boat in the middle of the ocean. And for anyone who was let down by the nonappearance of the titular character in “Witch,” this teensy-budgeted Sundance hit not only features plenty of sharks, they also happen to be real. The eerie trailer alone manages to make you want to throw up, scream, run away and stay glued to your seat, all at the same time.

Welcome to summer.