As questions still swirl about the six people found dead inside a baking-hot railway car in Texas, immigration advocates warn that the US is about to enter the most dangerous season of the year for immigrants making the perilous journey over the southern border.

Early results shared by the Webb county medical examiner indicate that at least one of the six people found dead in the city of Laredo died from hyperthermia, which occurs when the body is overwhelmed by extreme heat. The same cause of death is likely true for the five others.

The group of six, who ranged in age from 14 to 56, were all from either Mexico or Honduras. Laredo is home to a popular land port teeming with trade activity between Mexico and the US, leading investigators to believe early on that the deaths were the result of smuggling.

As of this writing, investigators believe immigrants boarded the Union Pacific train near Del Rio, Texas, before becoming trapped inside a sealed railcar during the journey to Laredo.

Paul Nixon, a retired teacher and volunteer with the Arizona-based humanitarian organization Green Valley-Sahuarita Samaritans, said he understands the allure of hiring a smuggler to help you board a train for the US – even if the dangers are extremely high.

“We’ve talked to people who have just had brutal on-foot overland travel with so much cartel abuse, [so] if there was an alternative, it just seems to me that that might be one of the things that people would do,” Nixon said. He added that another potential benefit of immigrating via train is avoiding the blistering heat that’s worsening in states like Arizona.

“But people will get into a boxcar and somebody will close the door and just forget that they’re there,” he said. “I mean, that’s a death sentence right there.”

According to non-profits like Humane Borders and No More Deaths, as well as data collected by Pima county, Arizona, hundreds of people die each year in the borderlands of northern Mexico and the southern US, though the true number is unknown. A large share of those deaths are related to scorching temperatures, which can regularly reach 118F in places like the Sonoran desert – a frequent route for immigrants bound for Arizona.

Laurie Cantillo, board chair for the Tucson-based Humane Borders, said most heat-related deaths occur from May to September, with July being the peak month. Her non-profit educates the public about border-crossing deaths and maintains water stations for immigrants making the perilous journey through the Sonoran desert.

A day after news broke about the deaths in Laredo, Cantillo was hosting a heat-awareness training for roughly 25 volunteers.

“What happened in Laredo is the most painful reminder that many of the victims of heat are children, young children,” she said, referring to the 14-year-old boy who was among the six people found dead on the railway car in Texas. “Heat exposure and dehydration is a horrible way to die. People become confused. Their skin becomes parched and dark in color. They may start tearing clothes off. They’re delusional; they drink their urine.”

Cantillo has seen these symptoms up close and personal. A couple of years ago, she and her fellow volunteers encountered a group of about two dozen Indigenous Ecuadoreans who were seeking asylum in the US and walking through the desert in 100F heat.

“They were huddled against the border wall, trying to take advantage of what meager shade it provided,” Cantillo recalled.

The group, who had no food or water, included a pregnant woman and another woman who was nursing a baby. Some people in the group were vomiting from the heat, a key symptom that hyperthermia is settling in.

Cantillo’s group identified themselves and provided bottles of water and wet bandanas. A short time later, border patrol agents arrived and took the people away.

“I was shaken by the experience and what might have happened had we and the border patrol not come along,” Cantillo said. “It’s a day I will never forget.”

Cantillo is friends with Dora Rodriguez, one of the best-known immigrant rights activists in Arizona. In July of 1980, the then 19-year-old Rodriguez survived one of the deadliest immigrant desert tragedies in modern border history.

After fleeing an El Salvador ruptured by civil war, Rodriguez and 25 other people became lost in the Arizona desert for five days in temperatures above 110F; their smuggler didn’t know which way to turn. Thirteen people died before border patrol agents rescued the survivors near Arizona’s Organ Pipe region.

A widely circulated Associated Press photograph showed a barely conscious Rodriguez being carried to safety by a border patrol agent.

“This is how hell feels,” Rodriguez remembered thinking. “Your body is just screaming for water.”

But according to critics of the agency, border patrol is often another obstacle immigrants must face during a potentially deadly trek through the desert – and not just because of the fear of being caught.

Jenn Budd, a former border patrol agent turned immigrant rights activist, said that, once they enter the field, agents are taught to vandalize water jugs left in the desert by groups like Cantillo’s. Cantillo said her group frequently deals with far-right militias doing the same type of vandalism.

“The literal education that you get in the field from this is it allows them to further their invasion into our country,” Budd said. “And if they really need water at any given time, they could just hit one of those 911 beacons or use their cell phone to call us, and we’ll go save them.”

In response to these claims, a spokesperson from border patrol said that agents act with “integrity”.

“Agents frequently risk their own lives to save the lives of illegal aliens in distress and carry extra water, electrolyte packets, sunscreen and cooling packs to provide immediate help to individuals suffering the effects of extreme heat,” the spokesperson said. “The US border patrol reiterates that the border is closed and that the dangers of heat exposure can be easily avoided by not crossing the border illegally.”

Claims that “the border is closed” fall apart in the face of border patrol’s own data, which shows thousands of “apprehensions” – including the apprehension of immigrants inside the US – happening each month so far in 2026.

Rather than being turned away by a closed border, veteran borderlands volunteers say that immigrants are being pushed further into dangerous parts of the desert. Once there, they are more likely to suffer from dehydration and exposure to extreme heat. This persistent policy is what’s known as “prevention through deterrence”, or the act of making a border crossing extremely difficult.

Nixon, the Green Valley-Sahuarita Samaritans volunteer, and his wife, Laurel Grindy, have gone on humanitarian journeys into the borderlands for the last eight years. They call “prevention through deterrence” policies “deterrence through death”.

The couple and their fellow Samaritans drive remote desert roads in southern Arizona, searching for immigrants in distress and leaving water, food, shoes and emergency supplies along known crossing routes.

“Right along the end of the border wall where we used to meet quite a few people each day, there’s just miles of concertina wire,” Nixon said. “The net effect of that is that they are forcing people farther and farther away from ports of entry and into wilder and wilder country. That’s what it’s been since Bill Clinton’s presidency: make people go the long way, make them suffer, let them die.”

Even though Nixon, Grindy and multiple other volunteers say that sightings in the borderlands have gone down, people are still clearly seeking a better life in the US.

A new report from the University of California at Berkeley Law’s Human Rights Clinic shows that climate change is acting as a “threat multiplier” in Central America, intensifying the poverty, food insecurity and violence that already drive immigration.

Based on surveys of immigrants in Mexico, the study found that most respondents had experienced multiple climate disasters – including hurricanes, heatwaves, droughts and flooding – before leaving home.

“The impacts of climate change – the health impacts and the disasters – leave people in greater and greater precarity,” said Helen Kerwin, one of the study’s authors. “They leave them less able to be resilient in place, and migration is the viable option.”

Because of deeply inadequate responses to climate change, activists like Rodriguez worry its status as a threat multiplier will only worsen, driving more people to the US regardless of the dangers posed by extreme heat.

This, she worries, could turn the desert in and around her new home of Arizona into “more of a graveyard”.

“When people understand what the heat does to you, it’s not something you’d wish on your worst enemy,” she said. “But people keep coming, so what does that tell you?”