By Hollywood’s calendar, summer apparently will kick off in April this year, but the studios already have heat stroke.Beginning with the April 25 launch of Fox’s “Volcano,” the majors will unleash a lava flow of mega-budget pics to the domestic marketplace, with unprecedented outlays for marketing, overtime fees on post-production and tranquilizers as producers and directors rush to meet release dates. And while chances are the number of wide releases will be comparable to last year’s 46, the risks this year are cosmic. Just take the July 4 weekend of last year, when Fox launched “Inde-pendence Day” and Buena Vista debuted “Phenomenon.” The combined budgets for the films: $103 million. This year, the two openers for that holiday are Sony’s “Men in Black” and Par’s “Titanic.” The budgets: $215 million, or more than double last year’s duo. After “Volcano’s” April bow, Par gets a jump on the summer on May 2 with “The Flood,” followed by the May 9 opening of Warner Bros.’ Robin Williams-Billy Crystal comedy “Father’s Day” and Sony’s “The Fifth Element.” That’s four big-budget hopefuls trying to leapfrog over the traditional start of summer, Memorial Day, when the behemoth that is “The Lost World: Jurassic Park” opens. The Universal pic kicks off the season’s huge number of sequels, which are hoped to have built-in audiences. It will be followed by Warner Bros.’ “Batman and Robin” and “Free Willy 3,” Fox’s “Speed 2: Cruise Control” and New Line’s “Mortal Kombat 2.” “Home Alone 3″ and “Alien Resurrection” are also on the summer slate, although they could be moved. But the increased presence of sequels doesn’t mean marketers at the studios can kick back and watch the receipts roll in this summer. No sure thing One producer reminded that the summer of 1989 was sequel-heavy, with such titles as “Ghostbusters II,” “Indiana Jones and the Last Crusade” and “Karate Kid III.” Their results varied and the biggest B.O. winner that year was a non-followup, the first “Batman.” “You can never take the consumer for granted,” says Chris Pula, Warner Bros.’ president of theatrical marketing. “There is a certain amount of brand awareness, but there is also a certain amount of cynicism, that there better be a value added reason for this movie’s being.” And the robust business of “Star Wars” — as well as other movies on recent weekends — has given some optimism to distributors, hoping that it will ride right on in to the warmer months. “I think we have already started it,” says Richard Cook, chairman of Walt Disney Motion Picture Group. “I’m not sure there will be any let-up at all between now and summer.” With budgets and marketing costs on the rise, distribs are engaged in an unprecedented amount of last-minute waiting, second-guessing and jockeying for position. Word came recently that Fox was ready to move up “Speed II: Cruise Control” from July 2 to the beginning or middle of June. That would put it into the same territory as Disney’s “Con Air,” slated for June 6. ‘Titanic’ may sail later There also has been buzz that “Titanic” could be pushed to later in July — either a week later to July 11, going against Warner Bros.’ “Contact” and Miramax’s “Wings of the Dove”; July 18 (when Disney has “George of the Jungle,” Miramax has “B Monkey” and New Line has “Money Talks”) or perhaps to July 25, when there are Sony’s “Air Force One,” Warner Bros.’ “The Conspiracy Theory” and “Wild America.” Only a few pics have established beachheads. U has “The Lost World” on May 23, with only New Line’s limited release of “Boogie Nights” skedded. Says New Line’s Mitch Goldman, president of distribution and marketing: “We benefit when we go against the grain, not with the grain.” Aside from some limited releases, WB’s “Batman and Robin” has the June 20 weekend to itself. BV has “Hercules” on June 27, with the wide competition so far being Par’s actioner “Face Off” and the Julia Roberts pic “My Best Friend’s Wedding” from TriStar. “It’s a nightmare,” says Jerry Bruckheimer, who has “Con Air” on June 6. “You’re lucky to get a weekend to establish yourself.” With its now-scheduled June 6 date, “Con Air” comes a week after “Lost World” and has two weekends’ breathing room between it and “Batman and Robin.” Bruckheimer adds that “Con Air” has been testing surprisingly high with women, a factor he attributes to Nic- olas Cage’s new star status. While he won’t discuss the marketing campaign, he says the film will be targeted individually to both males and females. But even if the crowd thins out, the inflated budgets already seem to have helped generate a huge marketing and merchandising push. “Is it getting bigger? Yes. Is it getting busier? Yes. But there is always going to be room for maneuvering, for counterprogramming, to be the sleeper of the season,” says Peter Dang, executive vice president of worldwide merchandising, licensing and consumer products for Sony Signatures. “Being crowded is nothing new,” says Harold Vogel, an analyst for Cowen & Co. in New York. “But the expense is so high that the risk is much higher.” U seems to be staking much of its synergistic future on the “Jurassic Park” franchise. A new team in the merchandising division has been established to help advise stores on displays. The marketing experts “are all extremely good at what they do,” says Tom Sherak, chairman of 20th Domestic Film Group. “They are all very talented people. But they are all going to earn their money this summer.” But the sheer wealth of sequels has some wondering if there will be overkill, giving an opening to other pics. And the same goes to marketing, with the risk that punch campaigns will leave the message lost. “It can get to be where they say ‘enough already,’ ” says Ivan Reitman, director of “Father’s Day.” “If you have too much of the same thing the audience feels manipulated.” New Line’s “Mortal Kombat 2″ debuts the first week of August, the same month as the original. Bruckheimer’s “Con Air” is skedded for June 6, the same weekend that “The Rock” debuted last year. (U’s “Leave It to Beaver” goes on the same date, as well as Miramax’s “Copland” and WB’s “187.”) “Mortal Kombat Annihilation” producer Larry Kasanoff says that even though ” ‘Mortal Kombat’ is the constant underdog, with the record companies, games companies and New Line, we get about $50 million in advertising by getting everyone in to spread the risk.” ‘Kombat’ ready Kasanoff says he likes his Aug. 1 spot because “you hope the early movies are huge hits, you do better by virtue of your predecessors doing great. Then people are amped to go to the movies.” Even “Men In Black” — a comedy actioner starring Will Smith and Tommy Lee Jones — has claimed July 2, the same weekend that “Independence Day” opened last year. “Given the power of the sequels being released and their creative elements, I think I would be a fool of underestimate their potential,” says Robert Levin, Sony president of worldwide marketing. “But I do believe that there is a grand opportunity for something unique and different.” July 4 fell on a Thursday last year, with studios opening films the day before to essentially create a five-day B.O. weekend. Studios are hoping to replicate that this year, by targeting their pics for bows on Wednesday, July 2. Yet the season has yet to generate much buzz around one particular picture, as “ID4″ had last year. Instead, much of the talk has been about the sheer magnitude of the budgets. One of the highest-profile pics is “Titanic,” which Par has domestically and Fox internationally. The buzz says that the pic’s bow would be pushed into later July to give director James Cameron more time to complete the megapic, although he is telling studio officials it will be ready. But even with a pricetag routinely bandied about at $135 million, the movie is unusual in other ways. There is little merchandising upside. It is not really an action movie, but a love story against the backdrop of boat and iceberg. And look at the storyline: “I heard it didn’t have a happy ending,” muses Vogel. But Par is poised to give it a marketing push that draws not only on the cachet of Cameron — who has used advanced special effects in each of his movies — but also on the youth appeal of stars Leonardo DiCaprio and Kate Winslet. Some exhibs are bullish on the product. “Everybody wants to throw stones at (Titanic’s) budget,” says Chuck Goldwater, president of Cinamerica Theatres, co-owned by Warner Bros. and Par. “But I don’t think that’s the story. The story is the quality of the films.” Last week, the posters appeared in theaters. The tag: “Collide with Destiny.” Hollywood execs are hoping that the summer collisions are minimal and that Destiny is kind.