The old men were staggering onto land, taking their first, wobbly steps away from the water’s edge.

The women had begun to nurse their babies, holding small, sea-kissed faces close to their fast-beating hearts.

And the giddy teenagers were busy snapping selfies to document their fleeting status as the newest refugee arrivals in Europe when the next rubber raft came motoring into shore.

Then another. And another.

If you want to understand the scale of the refugee crisis still to come in Europe, spend a few hours on this remote stretch of pebbly beach on the northern coast of the Greek island of Lesbos. Once a rare sight, today the flimsy boats roll in as ceaselessly as the tides, each one crammed with nearly 50 people.

On one recent day, the Coast Guard documented a record 4,500 arrivals from Turkey — nearly half the number from all of last year and part of a total for this year of 150,000 that makes this sublimely beautiful island in the Aegean the single most popular gateway to the European Union.

The numbers have spiked even as countries further north have slammed shut their borders, adding to a sense of urgency that the refugees can already feel in the shifting winds and the shorter days. Autumn is coming, and with it, rougher seas that will make this crossing far more treacherous.

“In a few weeks, the weather will be really bad,” said Hussein Hassan, a thin and bespectacled 23-year-old Syrian who, having landed on Greek soil, began his march from the sea in camouflage-themed Converse All Stars. “This is our last chance.”

And yet, the changing seasons may not actually serve as much of a deterrent. They may just add to the ever-rising toll of those who die trying to cross.

“Even on some of the worst weather days, when we don’t expect to see boats, people keep coming,” said Tyler Jump, spokesman for the International Rescue Committee, which has set up operations to help local authorities who freely admit they are completely outmatched by the extraordinary flows.

Greece became the main entry point for migrants fleeing to Europe this year because of the perceived safety of the route compared with the longer and more perilous journey across the central Mediterranean, from North Africa to Italy. In some places — including here on Lesbos — Greece and Turkey are separated from each other by as little as five miles, making for a speedy crossing that can be accomplished in as little as 45 minutes.

But the perceived safety of the route is fast yielding to the reality of choppier waves that can capsize an overcrowded raft in seconds. Across the Greek islands, the number of drownings has already begun to climb, with more people dying at sea in the past week than in the rest of the year combined.

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On Saturday, a 5-year-old girl drowned and 13 other migrants were feared lost at sea after their boat capsized off of Lesbos. Eleven other people were rescued.

The deaths were rare for Lesbos, which has seen fewer drownings than other islands. Yet, authorities say they worry that Saturday’s incident will be just the beginning if the massive flows continue into autumn and winter, when the number of crossings normally plummets. This year, the normal rules may not apply.

“What we’ve seen this year is something we’ve never seen before. So we don’t know,” said a weary-looking Lt. Cmdr. Antonios Sofiadelis, who leads Coast Guard operations in Lesbos.

Sofiadelis said he fears that the onset of autumn will simply mean more rescue operations for his overburdened forces, which are already conducting between 10 and 20 each day as boats stall out on the high seas and people are knocked overboard into the racing currents. For now, the water is warm by day; in a few months, it will be cold enough to kill day or night.

On the beaches, volunteer doctors say they are already starting to see more hypothermia cases in addition to the dehydrated patients they have been treating all summer.

“If the engine stalls out, it can take them three or four hours to get here. And at night, it’s getting very cold,” said Tali Shaltiel, a 31-year-old Israeli doctor who said she had treated everyone from a 2-week-old baby to a 95-year-old woman while tending to patients along the beach in recent days. “Some of them fall off the boat and are dragged the whole rest of the way.”

That didn’t happen to any of those who crossed here one recent morning. The sun was shining, the breezes were fair, and the Aegean was calm. It was a perfect day to cross, and those who did were acutely aware of their good fortune.

“I’ve reached Greece. I’m safe!” a joyful Hassan exulted into his cellphone minutes after his arrival.

“Thanks to God!” replied his mother, still trapped in a northern Syrian city besieged by the Islamic State. “I’ve been crying all morning. Now I’m so happy.”

Of course, Hassan’s journey had only begun. None of the new arrivals in Greece want to stay here; they all have their eyes fixed firmly on northern Europe. And with Hungary and Croatia blocking their path, it is unclear how they will get there.

Yet for the new arrivals, that hardly seemed to matter.

Hassan, who planned to travel to Germany so he could continue an education cut short by war, said he had heard that Hungary closed its border and that there were land mines in Croatia. But none of that gave him the slightest bit of hesitation.

“I’ve just crossed the sea,” he said with a young man’s bravado. “I’m not worried about anything.”

Indeed, many of those who crossed said they had been so focused on their terror of the open water that they had not had the chance to consider what would happen once they made it onto land. Some had only a vague idea of where they were.

“We just crossed from Turkey. Maybe we’re in Greece?” ventured 18-year-old Nadir Ali, a refugee from landlocked Afghanistan who caught his first-ever glimpse of the sea when he and 45 others shoved off into the aqua-green tides.

But getting off the island can be just as harrowing as getting on.

“We’re so tired,” said Sayed, a wheezing 60-year-old Iraqi imam who was still on the beach with his family, including a 2-year-old grandson, hours after their boat landed. “How far to the police station? Three kilometers?”

In fact, it’s a 40-mile trek from the north coast where most boats land to the camps in southeastern Lesbos, where all new arrivals are required to register. With only nine buses to transport the thousands of people who arrive daily, entire families can be seen walking along Lesbos’s steep, winding roads at all hours of day and night.

In the northern tourist village of Molyvos, where the ancient streets are made of cobblestone and shrouded from above by arbors threaded with grape vines, hundreds of people who are unable to make the walk sleep on the sidewalk, waiting for a ride.

Once people arrive at the camps, they find only rudimentary facilities, with too little food and too many other migrants packed into such a small area. Thousands choose instead to spend their nights at a tent city in the island’s main port, beneath a bronze Statue of Liberty that was modeled after the original.

Lesbos residents — many of whom are descended from refugees who fled Turkey in 1922 — have mostly been tolerant of the way the new arrivals have changed their island’s normally idyllic landscape. But there are signs that patience is wearing thin, especially as all-important tourism revenues decline.

“If other countries close their borders, where are these people going to go? They’re going to be stuck here in Greece,” said Abostolos Balzakis, a 55-year-old resident who watches the boats come ashore from his beat-up Suzuki pickup truck. “For the local economy, that will mean bankruptcy.”

At one point earlier this month, tensions on the island appeared set to boil over when the migrant population surged as high as 25,000. But the Greek government dispatched emergency help to clear the backlog, and police are now processing Syrian refugees within 24 hours. Others, including Afghans and Iraqis, still face a wait of up to a week.

Having arrived on humble dinghies, the refugees leave the island on chartered super-ships usually reserved for tourists, with capacities of up to 2,500.

As one left the port one recent day, its engines churning the placid waters, the refugees stood on deck waving and whistling. Then they turned forward to gaze at the open sea ahead.

Karla Adam in London contributed to this report.

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