The stacks of oversized, brightly colored envelopes and save-the-date postcards accumulating in recent weeks tell the story: The fall fund-raising season is about to begin. Some of the more organized individuals have already sorted through the invitations, filing them by date or pinning them up on bulletin boards already crowded with notices of fashion week parties and art gallery openings. Others have already crammed their BlackBerry calendars. But they keep on coming.

“I throw them all out,” Peter Gregory said at a party Friday in Southampton. It won’t do him much good. His wife, Jamee Gregory, is a fixture at charity balls, and he usually accompanies her.

“My housekeeper hides them from him,” Mrs. Gregory said.

Ready or not, here it comes: Monday through Thursday, and sometimes on the weekends, nonprofits are throwing parties. In New York, a town with 30,000 nonprofits, the galas are greater in number, more glamorous, and raise more money than in any other city in the world. And the range of missions they support seems infinite: They educate, feed the homeless, keep hospitals running, preserve great works of art, foster new artists and writers, and look for cures for cancer.

With the economy doing well, New York City charities are likely to have a record season, bringing in more than $100 million between now and December ($20 million alone is expected to come in on December 6 at the United Jewish Appeal-Federation of New York’s Wall Street Dinner). The fund-raising event calendar New York Masterplanner, published by Kintera, is listing 350 events in September and projects more than 1,500 to be listed through December, sometimes with more than 20 taking place on the same night.

The volume and scale of events means good times for hotels, caterers, designers, and florists. At the Waldorf-Astoria, where charity balls represent 37% of the hotel’s total banquet business, the grand ballroom is sold out for fall and almost booked for 2007. “This fall is likely to be a record in terms of revenues, and therefore most likely in charitable receipts,” the director of catering there, Jim Blauvelt, said.

A typical event at the hotel entertains 900 guests with the hotel charging $200 or more a person, and the charity charging $1,000 a person, with the goal of raising $1 million. More than 1,500 cocktails are served during the cocktail hour, most of them with vodka, and about 900 pigs in blankets.

Mr. Blauvelt estimates there are 3,000 to 4,000 “Waldorf regulars” who are the hotel several nights a week for charity events. “They’re right at home here. They know all the back doors.The waiters and captains know how many dinner rolls to give them or that they don’t like wine or they need a gin and tonic on the side. They’ve got a routine going,” Mr. Blauvelt said.

Spending on events is on the rise, supported by big donations, corporate underwriting, and luxury-brand gifts that raise the bar for the quality of party people expect. “The thing to note about this cycle is that it has none of the irresponsibility of the ’80s version of the cycle. It is considerate of the times, and considerate of what is truly responsible for the institution and not just for the small and privileged world of the benefit set,” Mr. Blauvelt said.

Organizations are handing off more to event-planning professionals, too. “What you’re seeing less of is that sort of committee of ladies, who expect a tasting from the caterer and a presentation of napkin samples,” event designer Bronson Van Wyck said. “Women are busier,” he said, “and not-for-profits realize that to maximize their revenue generation, volunteers ought to be on the phone calling their friends or their contacts through work… It’s such a better use of their time than debating the merits of peonies versus ranunculus.”

Some of the most glamorous and high-powered events, attracting the city’s top social and business leaders, are the ones supporting the city’s museums and performing arts institutions. The New York Philharmonic is first this year, opening its 165th season on September 13 at Avery Fisher Hall. The final opening of the season is the Tuesday before Thanksgiving at New York City Ballet.

City Opera traditionally comes first, holding its event the week after Labor Day, but it is moving to September 19 and featuring a one-time-only concert instead of an opera debut. “There are many artistic stories to tell at City Opera, and a challenging opera tells only one of those stories,” the director of development at City Opera, Jennifer Zaslow, said of the decision to change format, at the start of the final year of Paul Kellogg’s tenure at the company. “The Met is sending their message very loudly and we need to let people know about our history of innovation,” Ms. Zaslow said.The fund-raising goal is $700,000.

Meanwhile, the Metropolitan Opera will raise several million dollars at its opening night gala September 25, which is abandoning its concert format to feature the new production of “Madama Butterfly” directed by Anthony Minghella. Marking the start of the new general manager, Peter Gelb, the opera is planning on its biggest gala ever, honoring its biggest individual donors ever: Sid and Mercedes Bass, who gave $25 million last winter. (The Basses are also major supporters of Carnegie Hall’s opening night on October 4.) So many tickets have been sold to the opera gala that the supper has been moved to a tent in Damrosch Park from the Grand Tier. And that means that the longtime caterer of the event, Glorious Food, is out, and Lincoln Center’s caterer, Restaurant Associates, is in.

Organizations like to mark transitions at their galas. The downtown branch of the Smithsonian’s National Museum of the American Indian will cut the ribbon on the Diker Pavilion, a new 6,000-square-foot exhibition hall, at its gala on September 20. The next night, at the Chamber Music Society of Lincoln Center event, guests will toast the founder, Charles Wadsworth, as well as the new directors, David Finckel and Wu Han, who are presenting the first season completely under their creative control. The Whitney Museum will be gearing up for a major capital campaign to fund its recently approved expansion at its gala on October 23. The Fashion Institute of Technology is aiming to raise its profile with its first Couture Council Award, which will be presented to Ralph Rucci on October 19.

Inevitably, institutions wind up competing for attendees, corporate support, and venues. The Metropolitan Opera goes head to head with the mayor at the Fete de Swifty party, a gussied up block party on Lexington Avenue that hopes to raise $700,000 for the Family Justice Initiative of the Mayor’s Fund to Advance New York City. Liz Smith, one of the Fete’s founders, is not worried.

“You’ll always have some competition; New York is now so overbooked,” Ms. Smith said. “In our case, we get a lot of crossovers because we’re not a sit down dinner, you can come and stay a few minutes.” It’s not unheard of for guests with obligations at two events on the same night to go to one for cocktails and one for dinner.

Sometimes several of New York’s most beloved institutions go head to head, as on November 13, when the New York Public Library presents its Library Lions medal; WNYC brings in the host and producer of “This American Life,” Ira Glass, Jazz at Lincoln Center marks its second anniversary (and third gala) at the Time Warner Center, Lenox Hill Hospital kicks off its 150th anniversary celebration with a gala honoring maestro James Levine, who had his shoulder surgery there, and the Metropolitan Museum of Art gathers its supporters in the real estate industry.

One event making a major change in venue is the Studio Museum in Harlem’s gala on October 30. In just a few years, it has become a multimillion dollar fund-raiser with more than 1,000 guests. And so it is moving to the big-time Cipriani 42nd Street from the Metropolitan Pavilion in Chelsea.

Don’t think you can take a break to trick or treat. On October 31, the New York Restoration Project has its “Hulaween” ball at the Waldorf-Astoria and the Landmarks Conservancy honors Living Landmarks, including Barry Diller and Diane von Furstenberg and Amy and Howard Rubenstein, at Cipriani 42nd Street.

All the partying comes at a cost. The serious socialite can expect to spend $250,000 a year on jewelry, dresses, hair, and contributions, a publicist for charity events, R. Couri Hay, said. Perhaps that figure also includes his fees; he has a roster of socialite clients who pay him to ensure they are at the best parties.

But the socialites represent only a fraction of the total number of charity ball guests, who are motivated for a variety of reasons. For some, these events are a civic responsibility; for others, they are an extension of the workday. Still others attend events to maintain personal relationships.

A regular guest and planner of such affairs, for the Central Park Conservancy, Women in Need, and others, Gillian Miniter, said, “For the circuit to keep going, the parties must be fun, and they must support nonprofits that are using the money smartly and making a real impact on the city.”