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Credit Ruth Fremson/The New York Times

There are rules, at least unofficial ones, dictating that summer ends this weekend.

In New York, I can no longer swim outdoor laps at Tompkins Square Park or McCarren Park, and the lifeguards who patrolled the beaches at Cedar Grove or Wolfe’s Pond won’t be there to save me from drowning.

No more “Chinatown” on the big screen in Bryant Park (the last free movie was Aug. 24); no more Lincoln Center Out of Doors (Lyle Lovett was the closing act on, crazily, Aug. 9). Sommeliers look a bit shocked if I order a pretty pink rosé, and although I’ve tried to defy it, my mother’s commandment about the gaucherie of wearing white after Labor Day haunts me.

According to the autumn equinox, fall doesn’t begin until Sept. 23, and summer as a state of mind should last as long as the actual season, but culturally, it’s “sayonara” after the first Monday in September. Why are we in such a hurry to end this laconic time of year when, as George Gershwin wrote, “the livin’ is easy”?

I can buy corn and tomatoes at the farmers’ markets for several more weeks, and it stays light long enough for an alfresco supper — daylight time won’t impose its dreaded gloom until Nov. 1.

Tom Cruise is still on an impossible mission at the local cineplex, and while I’m not sure I could bear another moment without Stephen Colbert, we have weeks to wait for most grown-up movies and must-see TV. My air-conditioning bill is still stratospheric — so why are we taking our tweeds out of mothballs?

The reason may have something to do with our predilection for new tweeds. “I think it’s a marketing issue: more time to get us interested in pulling out our wallets for new clothes,” said Valerie Monroe, the beauty director of O the Oprah Magazine. “I’ve always loved the promise of the first cool snap while it’s still feeling lush and slightly oppressive. Maybe I’ve been seduced because of the marketing, especially of fall clothes. But if so, it’s worked.”

Friends and family can divide into Team Summer and Team Fall. “My wife and I have this ongoing jokey argument about when seasons change,” said Jason Rosenbaum, an assistant principal in Brooklyn. “I insist on the calendar as determined by astronomy, and she insists on merely one’s experience of climate shift: Summer ends when it is no longer very hot outside. Very ambiguous and variable. No one in our house can refer to the end of summer without treading into sensitive territory.”

We could certainly blame our children for the disconnect between custom and calendar. Even those of us without kids operate on a back-to-school schedule, and I got a lot of private messages telling me I was insane to think that any parent wants summer to last a minute longer.

“I love summertime,” said Erika Lenkert, an editor in San Rafael, Calif. “But I’m a full-time working mom, and I don’t have a nanny. Creating the fantasy of the playful, endless summer of childhood is totally exhausting. When school starts again, I’m wistful and relieved.”

I flirted with Team Fall this year after one of the hottest Augusts on record. That seems to be the month that kills us or makes us stronger. Part of me is tempted by visions of pumpkin-spice lattes and the knowledge that Oneg Heimishe in Williamsburg will reopen to bake chocolate babka (which, if it falls on your foot, your foot should break).

But how can I give up Jersey peach juice running down my chin?

William Leeds, an architect in New York City, thinks there may be some common cultural imperative to turn away from pleasurable things. Labor Day means “get back to work,” although in countries that don’t commemorate that holiday, there’s less willingness (or urgency) to be more serious. “It’s the rat race that everyone wants to get back into, and the herding instinct,” he said. “People have a problem enjoying themselves, especially Americans.”

Alex Knight, a technology and media investor in Seattle, has a slightly more dystopian view. “This year, rather than enjoying the final days of summer, people seem to be bracing themselves early for the inevitable nuttiness of the U.S. election and the unpredictable onslaught of climate change,” he said. “It’s a ‘rip the bandage off and let’s get on with it’ kind of moment. If you sense that you’re heading into an inevitable storm and the only way out is to go through it, you eventually have the urge to accelerate into it.

“Or maybe we just want ‘Downton Abbey’ to start sooner.”