In what has been billed as the biggest commercial airlift of horses ever, several hundred equine athletes have just been transported across the Atlantic to tiny Tryon, N.C. (two-legged population fewer than 2,000). Many flew in on round-trip tickets aboard specially appointed Boeing 777s and are now stabled in a state being drenched in the aftermath of Hurricane Florence.

The World Equestrian Games (WEG), an equine extravaganza that occurs every four years, runs from Sept. 11 to 23, a carefully choreographed 13-day schedule involving more than 8oo horses from more than 70 countries in eight disciplines, some of which are qualifiers for the 2020 Tokyo Olympics and all requiring special baggage allowances for equine paraphernalia, such as tail coats, top hats, cowboy boots and even carriages for competitive driving.

The storm is adding unpredictability to a complex logistical challenge: A whole day of competition has been called off, and a few animals will fly back without completing their contests.

It’s not yet clear what effect Florence will have on attendance, which organizers estimated could reach 400,000 — providing an economic boost to the region and helping realize a goal of Mark Bellissimo, co-founder and chief executive of the Tryon International Equestrian Center (TIEC), who also has facilities in Florida and Colorado and has ambitions to turn rarefied equestrian events into popular spectator sports.

WEG officials issued a news release describing a “robust” emergency response with an on-site weather station and “sheltering points for personnel and horses.” The TIEC facility was used as “a refuge for horses from five states” last year, ahead of Hurricane Irma.

But before competitions began, posts circulated on social media showing that some grooms had arrived to discover that although 1,288 permanent stalls had been built to withstand 90-mile-per-hour winds for their charges, some of them might have to bunk in dormitory-style tents.

“It looks like a concentration camp. But those are individuals who literally spend 20 hours a day with the horses,” said Packy McGaughan, a trainer. “So their accommodation has always tended to be sparse.”

Bellissimo issued an apology.

Headaches continued as the state’s response to Florence ramped up, threatening to undo some of the carefully laid groundwork, including extensive medical facilities brought into a rural Polk County community that typically has only three ambulances.

“We’d be quadrupling the population on given days,” said Mark Hart, the chief medical officer, who arranged for an onsite 14-bed hospital with two operating rooms, two emergency room doctors, and seven nurses who can perform X-rays and take bloodwork, and with generators and supplies that allow it to be self-sustained for a week.

With Florence — and opening ceremonies — looming, state officials considered recalling the hospital for use in worse-hit areas. But Med-1 was able to stay in Tryon on pre-deployment status until Friday, when it left for hard-hit Wilmington, N.C., and Hart turned to Plan B in a covered arena.

“This event is a big deal for the state of North Carolina,” he said. “They want to show their hospitality, and we understand the disaster that [they] may be looking at.”

There have been many bright moments for U.S. competitors — a gold medal in the cowboy skills called “reining” and silver in the horse ballet of dressage — and spectacular displays of equine agility.

The second phase of a tri-part contest known as three-day eventing took place on Saturday, just before the anticipated downpour. Horses galloped for 3½ miles through invigorating breezes, over an elaborate obstacle course created by Capt. Mark Phillips, former husband of Britain’s Princess Anne (both Olympians of an earlier era).

But as Florence approached, leaving inundation in its wake, Sunday’s entire schedule was called off, even though the slow-moving storm delivered little more than mist in the morning.

“The English would have been having a picnic in it,” McGaughan said.

Now, the third phase of three-day eventing will be pushed back a day until Monday, “changing the essence of the sport,” said U.S. rider Marilyn Little, who described how the schedule change could work to some competitors’ advantage.

Some top dressage horses, scheduled to fly out Monday, will forgo the popular freestyle segments of their displays.

“Horse welfare has to be the top priority and flying the horses out on the same day as competition doesn’t work,” Michael Stone, the Tryon 2018 organizing committee president, said in a statement.

Organizers had reason to be risk-averse as Florence threatened.

One of the first contests — endurance riding — met with tragedy when pre-hurricane heat and humidity took a toll. The contest began with a false start, after some competitors set off in the wrong direction along the 75-mile course. One horse — a New Zealand entry named Barack Obama — had to be removed and was later euthanized.

Tempers flared, and the weather deteriorated: One judge from the United Arab Emirates began live-streaming the altercations, showing police arriving to maintain order. After the skies opened, creating risky conditions under-hoof, veterinarians called off the entire competition.