As a traveler who prefers the off-season for its more affordable prices and fewer visitors, I try not to fly in July and August, at least in the Northern Hemisphere. I wait until fall when rates for flights and hotels normally plunge and crowds shrink.

Or they used to.

This year, hotels in Florence, Italy, in September were charging close to summer highs. I was priced out of Key West, Fla., in November, a historically slow month. Considering the eco-friendly resort Playa Viva near Zihuatanejo, Mexico, for the first week of December — long a bargain time to travel — I could find only one night available at rates below $500.

What, I wondered, happened to the off-season?

“September is the new August,” said Jack Ezon, the founder of Embark Beyond, a high-end travel agency based in New York City, explaining that the frenzy for European travel stretched the calendar. Nearly a third of his clients who regularly travel to the Mediterranean in July and August rescheduled for June, September or October.

“People are making choices to avoid the crowds and the heat,” said Virgi Schiffino Kennedy, the founder of Lux Voyage, a travel agency based in Philadelphia.

“I’m seeing summer rates creeping into shoulder season,” she added, noting that destinations like Santorini and Mykonos in Greece, which peak in July and August, “are now impossible to book in September.”

School calendars still largely dictate the biggest peaks in travel annually, but the dips are not as dramatic — in numbers and in rates.

“I think we’re at the beginning of a change,” said Henry Harteveldt, a travel industry analyst who runs the firm Atmosphere Research Group based in San Francisco, crediting flexible work schedules for the trend. “Summer will always be peak season, but I think we’ll see more off-peak travel in fall, winter and spring so those valleys may be less deep.”

The shoulder season surge

Travel is most certainly back — the World Travel & Tourism Council said the industry will recover 95 percent of 2019 activity this year — but it’s not a replica of prepandemic patterns.

Compared to 2019, global leisure stays were up 12 percent in spring 2023 at more than 230 Sofitel and MGallery hotels. Fall 2022 bookings were up 7 percent for leisure guests compared to the same period prepandemic.

“Booking shoulder season was once travel’s best-kept secret, but more people are catching on to the trend,” said Matt Berna, the president for the Americas of Intrepid Travel, a global tour company. He said fall and spring bookings this year have grown by 56 and 70 percent, respectively, compared to prepandemic business, inspiring the company to increase its departures to meet the demand.

The river cruise line AmaWaterways has done the same, adding new itineraries for November and February.

G Adventures, which offers small-group trips, said bookings by Americans are up 40 percent this year over 2019. When summer trips in Italy sell out, travelers are bound to look deeper into the calendar, said Steve Lima, the vice president of growth for the U.S. and Latin America for G Adventures.

“It’s like Disney’s always busy and there’s no good time, so you just go,” Mr. Lima said.

Katie Parla, a Rome-based cookbook author who guides private food tours, described a pig-in-the-pipeline scenario where travelers who booked a tour for their 35th wedding anniversary weren’t able to take it until their 37th because of travel restrictions and complications over the past few years.

“The high season used to be Easter to October, but this year Rome started to be slammed a full month earlier and my calendar is nearly full through the end of December already, which is very rare,” Ms. Parla said.

The seasonal switch isn’t just a European phenomenon. Apple Leisure Group, which offers value-priced vacation packages in Mexico and the Caribbean, has seen bookings more evenly distributed throughout the year over the past three years. As a result, its prices are more consistent year-round.

In an August report, Kampgrounds of America found 67 percent of campers had changed their travel plans this year because of the weather. Nearly 64 percent of campers who delayed trips planned to take them after Labor Day. The R.V. rental platform RVShare said shoulder season reservations have grown twice as fast as those in their core summer season, which it attributes to flexible work policies and efforts to avoid extreme heat.

Claire Ramsdell, 31, who works nomadically in customer service for an outdoor company and blogs about hiking, spent the summer in Bozeman, Mont., but found it too hot to work from her vehicle, forcing her to rent high-price accommodations with roommates and poor Wi-Fi.

“I’m not sure why I tried to branch out and do such a popular and expensive destination this summer,” she wrote in an email from Colorado where she plans to hike this fall. “I should go back to off-season travel and less-crowded places.”

The rule of school

In a recent travel forecast from Expedia, 70 percent of fall travelers are adults without children.

“We have the flexibility to get the cheapest flights and hotels and not wait in line at the Vatican, sweating with the summer crowds,” said Riana Ang-Canning, 31, of Vancouver, Canada, who works in social media and travels off-season with her husband extensively.

Resolving to avoid summer’s high prices and heavy traffic is easier said than done for families with school-age children, but some parents are considering workarounds.

Before the pandemic, Jennifer Glaisek Ferguson, a mother of two children ages 5 and 8 in Weston, Conn., and her family took a midsummer trip to France when it was sweltering, which they vowed not to repeat. The importance of school attendance and keeping up with the curriculum has deterred the family from skipping much school for travel, but she’s open to missing a few days.

“When there’s an opportunity to see something new and different where they can learn, I’m willing to take the hit,” Ms. Ferguson, 53, said.

Ms. Schiffino Kennedy of Lux Voyage said her family clients tend to add a day or two onto long weekends.

“Clients call with their school calendar in front of them looking to make the most of holidays,” she said, noting that she does the same; this Indigenous Peoples’ Day on Oct. 9, she plans to take her 9-year-old daughter out of school a few extra days to take a five-day trip to Sedona, Ariz., and the Grand Canyon.

Misty Belles, the vice president of global public relations at the travel agency consortium Virtuoso, predicted the return of the rule of school may fuel bookings in late spring, just as classes end.

“Normally in Europe, travel doesn’t start until mid-June, but I think we’ll see many trying to get there early before the heat is a factor,” Ms. Belles said.

Selling ‘secret’ season

Business-wise, the erosion of troughs in the booking calendar is intentional. Travel marketers have long pushed “green season,” May through November, in Costa Rica when it’s rainy but lush, and “cabernet season” in Napa Valley, November through April, when things slow down and restaurant reservations at the French Laundry may be easier to nab.

Montreal en Lumière, an annual winter festival, was established 25 years ago as a way to encourage travel to the Canadian city in a slow period. Last year, the 18-day midwinter festival drew nearly 800,000 attendees to its ice rinks and concerts. Participating restaurants were booked to 96 percent capacity.

To encourage off-season visits on Cape Cod, Pelham Hospitality, which operates three hotels, has introduced activities like indoor roller skating. Chatham Bars Inn calls September and October “secret summer” with programming, including dinner at the property’s nearby eight-acre farm.

“As a destination, minimizing occupancy ‘valleys’ is important for maintaining year-round employment to support tourism businesses and a high-quality experience for travelers,” wrote Bill Lewis, the general manager of the Magnolia Hotel & Spa in Victoria, British Columbia, and chair of the Victoria Hotel Association, in an email.

Whether it’s the relative quiet, the deals or the weather, off-season conditions have gained their own renown, said Andrew Lloyd, the director of Lloyd & Townsend Rose, an agency that specializes in renting castles and estates in Britain and Ireland.

“I don’t believe there is any longer an off-season,” he said, noting that the special light in the winter months draws photographers to Scotland. “I am constantly amazed how busy places are during so-called off-season months and ultimately one realizes, the world is now a very busy place.”

Downsizing slow seasons

Crowd-averse die-hards, like me, will brave Iceland in the snow, despite the dangerous driving, and visit Homer, Alaska, in October when half the shops are closed. I can have things my way: quieter, cheaper, more local.

“My love of off-season travel is rooted in being frugal, but I also cannot do the heat and would rather see the mountains when it’s 30 or 40 degrees rather than 80 or 90,” said Heather Bien, 38, a writer, blogger and marketer based in Washington, D.C., who is planning to stay in a glamping tent in North Carolina in December.

For folks without that kind of fortitude, it’s time to stop thinking about seasons as months and instead as weeks or even days. These micro-shoulders still exist in many places in November — excluding Thanksgiving week — the first few weeks in December and, outside of ski destinations, in January and February.

For best results, go off-peak Monday through Thursday. At Four Sisters Inns, a collection of 17 boutique hotels in California, the lowest rates are available midweek during winter and early spring.

“The new shoulder season in Europe is winter,” said Jonathan Alder, the founder of Jonathan’s Travels, an agency based in Winter Park, Fla. “To be there when its 30 to 50 percent cheaper and no crowds, go to Rome in January.”

On Lake Como in Northern Italy, the Grand Hotel Tremezzo touts October as an ideal time to visit, when the weather is fair, the crowds disperse and rates are less than half of high season (starting at $825 a night compared to $1,870 in summer). But it’s a short window. The hotel closes for the 2023 season on Nov. 5.

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