Nicholas Gubell was nearing the end of his route on Long Island when he began to feel unwell.

About 200 packages were delivered by Mr. Gubell. He would spend up to a minute or so to get his cargo out of the metal shell of the back of the truck, which was very hot.

He was barely able to speak after being pulled over on the side of the road.

Mr. Gubell stated that his body was losing it. Paramedics took him to a hospital after covering him in ice packs. He said he was trying to hold on.

Nick Gubell, a driver for UPS, was hospitalized several weeks ago after suffering severe heat exhaustion while on the job.Credit...Johnny Milano for The New York Times

Mr. Gubell has continued to deliver America's packages for a variety of carriers, often in trucks that have no cooling mechanisms for drivers, because of the heat waves. There are photographs that show the temperature in the back of the trucks.

A number of heat-related illnesses among the drivers has renewed calls for improved working conditions.

The president of a Texas local of the International Brotherhood of Teamsters said that many of his workers were sick. He said it was terrible.

According to government records, at least 270 United Parcel Service and United States Postal Service drivers have been sick and hospitalized from heat exposure in the last three years. Dozens of workers for other delivery companies have also suffered from heat exhaustion, according to the records, and a few drivers have also died in the past few years. There are heat-related injuries and illnesses that are under reported.

The Center for Public Integrity and NBC News reported on the dangers mail and delivery workers face in the heat.

The union has been preparing for better protection for the workers of the package delivery company. "With the temperatures and the record heat waves, it's getting to the point where we are getting an alarming amount of heat- related injuries."

18 workers in his jurisdiction have become sick by the heat in the past six weeks. He said that the situation is getting worse.

Scientists agree that heat waves around the world are becoming hotter and more frequent as a result of climate change. In the United States, the number of hot days is increasing, according to the National Climate Assessment, a major scientific report by 13 federal agencies. The 1960's heat wave season was 45 days longer than it is today.

Co-workers at the funeral of Esteban David Chavez Jr., who died in the back of his UPS truck in Pasadena, Calif., in July.Credit...Dominique Chavez

Jose Cruz Rodriguez Jr., a driver for United Parcel Service, was found dead in the company's parking lot in Texas just days after he started work. The driver of a package delivery vehicle died in Pasadena, Calif., about 10 miles from downtown Los Angeles. A worker for the company was caught on camera stumbling and collapsing outside of a home in Arizona.

While the Postal Service and other delivery drivers have been sick, attention has mostly been on United Parcel Service, which is the world's largest package delivery company. The company's delivery trucks don't have air-conditioning.

The company said that its package delivery vehicles make frequent stops, which requires the engine to be turned off and the doors to be opened and closed.

The health and safety of the employees is the highest priority of the company.

The company said it planned to distribute cooling towels and uniforms made of moisture-wicking fabric and to accelerate the installation of fans in vehicles. The company said that they don't want their employees to risk their health or work in an unsafe way.

Lawmakers want better conditions for mail carriers.

Tony Crdenas, a democrat from California, introduced a bill last month that would require the postal service to install air-conditioning in all of its vehicles. The measure is named after a mail driver who was found unresponsive in her truck in the San Fernando Valley on a day when it was 117 degrees outside.

More than half of the Postal Service's vehicles have fans, and 34 percent have air-conditioning. The postal service said that their carriers deliver the mail throughout the year. During the summer months, the temperatures rise.

The service said that it started a heat illness prevention program to provide mail carriers with training and resources needed to do their jobs safely, and that it reminded carriers to stay hydrated, wear hats and get in the shade.

During the day, it said, it has sent reminders to "stay hydrated and to take their rest breaks."

The drivers said that they were insulted by the reminders. In an environment where bathroom breaks are limited to stops at stores and restaurants, it is hard to drink enough water.

Matt Leichenger, 26, delivering packages along his route in Brooklyn on Tuesday.Credit...Johnny Milano for The New York Times

The heat can still get to you even though you can drink gallons of water. He said the training tells you to eat cucumbers and watermelons.

Demands for shipping have gone up as temperatures have gone up. Drivers say that the coronaviruses kept shoppers at home and caused a surge in e- commerce.

Tony Bell is a U.P.S. driver in Texas. Mr. Bell was hospitalized after working his route on a 103 degree day.

He drank a lot of water and a drink. He said that doctors told him that he was close to death. He said he was afraid that was it.

Jorja Rodriguez said she gave her son a cooler full of water and energy drinks and told him to take it easy.

When Mr. Rodriguez didn't show up at home that night, she went to the store and watched as the police found his body.

Esteban David Chavez Jr.Credit...Dominique Chavez
A UPS banner at Esteban David Chavez Jr’s grave.Credit...Dominique Chavez

She thought that Mr. Rodriguez would wake up if she called his name so many times. Since her husband's death, the stepmother of Mr. Chavez has made a point of giving a tip and a drink to the workers.

On the day he felt unwell, Mr. Gubell was able to call his parents.

He was too incoherent to tell them where he was. The authorities were also notified by a neighbor. Mr. Gubell said he didn't want to call the ambulance because he was afraid of being retaliated against by the shipping company.

He said that people are dropping like flies outside. It is very vicious.

The email said that if one of their drivers needed immediate assistance, the company would send personnel to their location to help them safely return to the delivery center or arrange for immediate assistance at the driver's location.

Prudence Gubell regretted that she encouraged her son to apply for a job with United Parcel Service and never imagined that the job could be so dangerous.

Ms. Gubell worried about him. The human body can take a lot.

Rachel Shorey contributed to the report.