EL PASO, Texas — Along the southern border, two cities — El Paso, Texas, and Ciudad Juarez in Mexico — prepared Sunday for a surge of as many as 5,000 new migrants a day as pandemic-era immigration restrictions expire this week, setting in motion plans for emergency housing, food and other essentials.

On the Mexican side of the international border, only heaps of discarded clothes, shoes and backpacks remained Sunday morning on the banks of the Rio Grande, where until a couple of days ago hundreds of people were lining up to turn themselves in to American officials. 

One young man from Ecuador stood uncertain on the Mexican side; he asked two journalists if they knew anything about what would happen if he turned himself in without having a sponsor in America, and then gingerly removed sneakers and socks and hopped across the low water.

On the American side, by a small fence guarded by several Border Patrol vehicles, he joined a line of a dozen people who stood waiting with no American officials in sight.

An El Paso county judge, Ricardo Samaniego, told the Associated Press on Sunday that the region, home to one of the busiest border crossings in the country, was coordinating housing and relocation efforts with groups and other cities, as well as calling on the state and federal government for humanitarian help. 

The area is preparing for an onslaught of new arrivals that could double their daily numbers once public health rule Title 42 ends on Wednesday.

The rule has been used to deter more than 2.5 million migrants from crossing since March 2020.

At a migrant shelter not far from the river in a poor Ciudad Juárez neighborhood, Carmen Aros, 31, knew little about American policies. In fact, she said she’d heard the border might close on December 21.

She said she fled the cartel violence in the Mexican state of Zacatecas a month ago, right after her fifth daughter was born and her husband went missing. The Methodist pastor who runs the Buen Samaritano shelter put her on a list to be paroled into the United States and she waits every week to be called.

“They told me there was asylum in Juarez, but in truth, I didn’t know much,” she said on the bunk bed she shared with the girls. “We got here … and now let’s see if the government of the United States can resolve our case.”

At a vast shelter run by the Mexican government in a former Ciudad Juárez factory, dozens of migrants watched the World Cup final Sunday on two TVs while a visiting team of doctors from El Paso treated many who had come down with respiratory illness in the cold weather.

Constantly changing policies make it hard to plan, said the director of the Hope Border Institute, Dylan Corbett. The Catholic organization is helping migrants in both El Paso and Juarez. The group started the clinic two months ago.

“You have a lot of pent-up pain,” Mr. Corbett said. “I’m afraid of what’s going to happen.” With government policies in disarray, “the majority of the work falls to faith communities to pick up the pieces and deal with the consequences.”

Just a couple blocks across the border, sleet fell in El Paso as about 80 huddled migrants ate tacos that volunteers grilled up. Temperatures in the region were set to drop below freezing this week.

“We’re going to keep giving them as much as we have,” said Veronica Castorena, who came out with her husband with tortillas and ground beef as well as blankets for those who will likely sleep on the streets.

The owner of a trucking school in town, Jeff Petion, said this was his second time coming with employees to help migrants in the streets. “They’re out here, they’re cold, they’re hungry, so we wanted to let them know they’re not alone.

Across the street from Petion, Kathy Countiss, a retiree, said she worries the new arrivals will get out of control at El Paso, draining resources and directing enforcement away from criminals to those claiming asylum.

On Saturday, El Paso’s mayor, Oscar Leeser, issued an emergency declaration to access additional local and state resources for building shelters and other urgently needed aid.

Judge Samaniego said the order came one day after El Paso officials sent Governor Abbott a letter requesting humanitarian assistance for the region, adding that the request was for resources to help tend to and relocate the newly arriving migrants, not additional security forces.

Judge Samaniego said he has received no response to the request and plans to issue a similar county-wide emergency declaration specifying the kind of help the area needs if the city does not get state aid soon. He urged the state and federal governments to provide the additional money, adding they had a strategy in place but were short in financial, essential and volunteer resources.

El Paso officials have been coordinating with organizations to provide temporary housing for migrants while they are processed and given sponsors and relocate them to bigger cities where they can be flown or bused to their final destinations, Judge Samaniego said. 

As of Wednesday, they will all join forces at a one-stop emergency command center, Judge Samaniego said, similarly to their approach to the Covid emergency.

Mr. Abbott, El Paso city officials, and Customs and Border Protection did not immediately respond to requests for comment on Sunday.

Mr. Abbott has committed billions of dollars to “Operation Lone Star,” an unprecedented border security effort that has included busing migrants to so-called sanctuary cities like New York, Los Angeles, and Washington, D.C., as well as a massive presence of state troopers and National Guard along the Texas-Mexico border.

Additionally, the Republican Texas governor has pushed continued efforts to build President Trump’s wall using mostly private land along the border and crowdsourcing funds to help pay for it.

El Paso was the fifth-busiest of the Border Patrol’s nine sectors along the Mexico border as recently as March and suddenly became the most popular by far in October, jumping ahead of Del Rio, Texas, which itself had replaced Texas’ Rio Grande Valley as the busiest corridor at lightning-speed late last year. 

It is unclear why El Paso has become such a powerful magnet in recent months, drawing especially high numbers of migrants since September.

Recent illegal crossings at El Paso — at first largely dominated by Venezuelans and more recently by Nicaraguans — are reminiscent of a short period in 2019, when the westernmost reaches of Texas and eastern end of New Mexico were quickly overwhelmed with new arrivals from Cuba and Central America. El Paso had been a relatively sleepy area for illegal crossings for years.