Summer begins at midnight.

Spider-Man 3 swings into theaters at witching-hour screenings Friday, and with it comes the start of an 18-week-long blockbuster blowout.

From Friday through Labor Day weekend, Hollywood will roll out new models of Shrek, Pirates of the Caribbean, Fantastic Four, Harry Potter, Die Hard, George Clooney's Ocean's Eleven and Matt Damon's Jason Bourne spy series, along with Spider-Man 3 and Evan Almighty, an indirect direct descendant of Jim Carrey's Bruce Almighty, with Steve Carell.

Oh, and don't forget The Transformers, The Simpsons' big-screen debut, the new Adam Sandler comedy, I Now Pronounce You Chuck and Larry, and the season's contender for best buzz, Knocked Up.

Add them all up, and Exhibitor Relations Co.'s Jeff Bock predicts they'll add up to a lot of ticket sales.

"We're definitely talking about a summer box office of $4.5 billion," Bock estimates. "It's not ridiculous to say that number."

To put the prediction in perspective, last summer's movies combined to gross $3.7 billion. The hottest summer box office in history—2004's—was worth $3.8 billion.

Can this summer really be more than $1 billion bigger than the biggest one on record? The answer, or at least a good hint at it, could come as early as Sunday, when this weekend's estimates are released.

"Spider-Man 3 is definitely going to set the tone," Bock says. "Mission: Impossible III set the tone last year—it was a little lackluster."

So far, the early returns on Spider-Man 3 look good for Sony, in particular, and Hollywood, in general. The sequel is off to a hot start in Europe and Asia, where it opened Wednesday, outpacing both of its predecessors. Stateside, Fandango reported the movie was selling six times as many advance tickets as Spider-Man 2 was at this point in 2004. (Fandango and E! Networks are both subsidiaries of Comcast.)

Add the evidence up, and Box Office Mojo's Brandon Gray predicts the verdict will be a landmark one.

"Spider-Man 3 has an excellent chance of breaking the opening weekend record," Gray says. "[It's] a sequel people want to see because in general they liked the first two."

While Gray won't attach a dollar figure to his estimate, his guess that Spider-Man 3—opening at a record 4,252 theaters—will emerge with a title Sunday means he's thinking it'll snare somewhere north of $135.6 million. That's how much current record holder Pirates of the Caribbean: Dead Man's Chest looted audiences for last summer.

Beyond opening weekend, Gray says he thinks Spider-Man 3 has a shot to finish the season as the summer's number one movie. That's because, in part, it has the biggest open field of any of the top summer contenders—a whole two unfettered weeks, with apologies to Delta Farce and Lucky You—until Shrek the Third opens May 18. After Shrek, it's one big movie after another until things slow down in August.

If the expectations are huge for Spider-Man 3, it's because the first two movies were huge. The original Spider-Man, released in 2002, made $404.7 million (and another $418 million overseas), for seventh place on the list of Hollywood's all-time top moneymakers, per Box Office Mojo stats. Spider-Man 2 made $373.6 million (plus $410.2 million overseas), good for 10th on the list.

Starring Tobey Maguire and Kirsten Dunst, as the hero and his girl, respectively, Spider-Man 3 costars a host of villains: Thomas Haden Church as Sandman; Topher Grace as Venom; James Franco as New Goblin, offspring of the Green Goblin, who was played by Willem Dafoe in the first movie; Maguire, arguably, as the big, bad, meteorite-messed-with, black Spider-Man; and, if you consider the perspective of Dunst's Mary Jane, Bryce Dallas Howard as Gwen Stacy, Spidey's true love from the comics.

Review-wise, critics are responding to the largesse with all the enthusiasm of people obliged to sit through a 140-minute-long work assignment (yes, the movie really does clock in at two hours-plus, so pack your salty provisions accordingly).

"That's what Spider-Man 3 is all about: Piling it on," Tom Long writes in the Detroit News. "Maybe it's time for the franchise to take a few years, spin a few webs, catch a few flies and reconsider its approach. Because [this movie] is simply too much all at once to no good end."

The New Yorker's Anthony Lane calls the movie "a shambles," and, save for "one great scene" involving the advent of Sandman, "so embarrassing that you have to crouch down and stuff popcorn in your ears."

Noel Murray, writing for The Onion's A.V. Club, finds the movie's action "superb and its theme fairly weighty," which still isn't to say he's totally in love. He thinks the non-superhero-related comedy and drama falls flat.

To the rescue of Sony's marketing department comes Newsweek's David Ansen with the imminently blurbable: "Spider-Man 3 is all about quadrupling the fun."

So far, Ansen's judgment is more or less the prevailing one. At one point Thursday afternoon on the review-tracking site Rotten Tomatoes, Spider-Man 3's positive notices outnumbered the negative ones, 72 to 41.

The box-office returns, though, will best gauge the film's temperature. Not to mention the summer's.