Never in your life will you ever be as glad to see rain.

The occasion is "Singin' in the Rain" at the Paper Mill Playhouse. The much respected 1952 MGM musical movie was a tepid flop when turned into a Broadway show about a decade ago. But that didn't stop the Millburn showplace from scheduling it as its 1994-95 season opener.

And, truly, the Paper Mill is one of the few theaters in the country that could have even considered taking on such a daunting task as "Singin' in the Rain." After all, it not only requires some black-and-white live-action short subject films, but also many sprinklers and much drainage for that oh-so-famous rainy street scene.

That one number truly justifies putting "Singin' in the Rain" on stage. True, for the price of an orchestra seat, you could buy the movie at your local video store, and have enough money left over to purchase yet another film, popcorn, and jujubes. But watching Michael Gruber battle the elements for real and not on film is more thrilling. It sure was at Friday's opening, when his umbrella couldn't take the downpour and broke mid-number. But Gruber didn't break stride. He just tossed it away, and brought the number to a smashing conclusion without it. Fabulous.

Aficionados of the movie - and that includes everyone from Leonard Maltin to Francois Truffaut - will want to know if liberties have been taken with their beloved film. Yes and no. The story of silent film stars Don Lockwood and Lina Lamont who must make the transition to talkies - only to find that he can but she can't - retains virtually all the dialogue. There's also a new passably good joke about the Gettysburg Address, and a truly excellent one involving a key in which a song should be sung.

But that marvelous sequence when Gene Kelly drops into Debbie Reynolds' convertible while she's on her way to work isn't here. Instead, Don and Kathy meet while he's on foot, running away from his fans. Surprising that the usual spare-no-expense Paper Mill management didn't spring for a car. Where's that nifty auto that traversed through "Paper Moon" just a year ago?

As for the Nacio Herb Brown-Arthur Freed score, it's been augmented. The "You Are My Lucky Star" sequence that Reynolds filmed for the movie, only to have it dropped, is back in place. Lina has a number, too, "What's Wrong with Me?" in which she soliloquizes that there's nothing problematic with her voice. Unfortunately, there is, in the performance delivered by Deborah Jolly. It's one thing to do the dumb-blonde locutions, but far too often Jolly can't be understood. There was protracted silence after many of her punch lines. And they would have received laughs had the audience been able to decipher them.

One other song's been added. After Don rediscovers Kathy, he sings "You Stepped out of a Dream." No, what she really stepped out of was a cake, so this number doesn't work very well, despite Gruber's nice vocalizing.

Many may be snarling, "How can you begin to compare Michael Gruber with Gene Kelly, anyway?" Well, of course, you can't. Gruber isn't as rubber-legged, but he at least has a profile that's very much in keeping with what was considered movie-star material during the silent movie era. And for those who are ready to add, "Christina Saffran is no Debbie Reynolds," they should be apprised that Saffran does add a pinch more humanity to her Kathy. What's more, Saffran does have a lovely voice. Hearing her in this role of a voice-dubber makes you wish that some stage musicals would hire Saffran to sing for some so-called musical actresses.

As Don's best friend, Cosmo, - the Donald O'Connor role - Randy Rogel, seemingly no more than 5 feet tall, is most endearing. He must also take on "Make 'Em Laugh," certainly one of the most grueling tour-de-forces ever attempted on film. But if you watch the movie, you'll notice two splices during this number, leaving us to believe that O'Connor didn't do it from beginning to end in one take. Rogel, though, doesn't have the luxury of a director saying "Cut. Let's try it again." He must do it continuously before our very eyes, doing those somersaults and backflips, and taking the slings and arrows of outrageous walls and couches. Rogel manages it all marvelously, and didn't just make 'em laugh, but made 'em applaud twice before the number was over.

No, the cast's real problem isn't the way it performs, but how quickly it gets through the musical. Thus far, director James Rocco hasn't been able to extract the spritely pace of the film. Part of this is his fault for choosing blackouts to switch from one scene to the next. In the movie, a scene deftly blends into another with a quick dissolve. Rocco's blackouts aren't a problem when a scene ends with a song, but they certainly are when a line of dialogue bears the burden. While a dissolve doesn't place as much emphasis on the final line of a concluding scene, a blackout somehow suggests that the line we just heard is hilarious. Many in "Singing' in the Rain" aren't.

But Rocco, along with co-choreographer Linda Goodrich, has come up with some nice dance work. The "Temptation Tango" is stronger than its movie counterpart. And while the film's elaborate talking picture montage and "Broadway Melody" aren't as breathtaking, the team tackled the dream ballet - innovative in the '40s, trendy in the '50s, tired in the '60s, and dead in the '70s - and gave it renewed vigor.

Costume designer Gregg Barnes creates the gaudy idiocy of yesteryear with skill and panache. And scenic genius Michael Anania has once again come up with more opulence - maybe even too much, when one considers that he ordered two schoolroom sets when one seemingly would have served. But Anania was witty to include a scrim with the famous Hollywood sign stating "Hollywoodland," as it did in the days of the silents.

No, this "Singin' in the Rain" won't make you forget the movie. But the Paper Mill powers-that-be undoubtedly knew that from the beginning. The bottom line is, they weren't incorrect to think, "Isn't this a lovely play to be caught in the rain?"