FedEx spokesperson Adam Snyder says the company reminds contractors to closely monitor working conditions. “We encourage our team members and service providers across FedEx to take precautions in the hot weather by staying hydrated, taking frequent breaks, and recognizing the signs of heat related illnesses,” he says. UPS spokesperson Becky Biciolis-Pace says the company is increasing access to ice, water, and electrolyte drinks for drivers, and provides annual heat awareness training. The company also provides cooling sleeves and hats developed by a performance apparel company.

Heat stress can produce a range of symptoms, from muscle cramping due to electrolyte loss up through organ failure and death, says Brenda Jacklitsch, a health scientist at the National Institute for Occupational Safety and Health (NIOSH). Workers can be exposed to heat both from the environment and their own physical exertion like lifting boxes. High heat can affect the brain, interfering with signals it usually sends to blood vessels to dilate and cool the body. Humidity can prevent sweat from evaporating and transporting heat away from the skin, stopping the body from cooling itself.

The progression of symptoms, from dizziness or cramping to death, can unfold gradually or in as little as an hour, says Robert Harrison, a University of California, San Francisco physician and occupational health specialist who spoke at a press conference last week hosted by the Warehouse Worker Resource Center.

A lack of air-conditioning at home, which disproportionately impacts lower wage workers, can compound the problem after a worker’s shift is over. “If there’s not a place to cool down, many people become seriously ill,” Harrison says. A death at home would not be counted in work-related fatality numbers.

An analysis of US Occupational Safety and Health Administration data by The Washington Post found that seven delivery drivers died from heat stress between 2017 and 2022. The occupation ranked fifth among heat-related workplace deaths, behind construction, agriculture, landscaping, and roofing.

Health experts say that heat protection boils down to three basics: water, shade, and rest. Delivery drivers seeking those remedies can run into social pressure. When Gonzalez, the UPS driver, has ducked into air-conditioned businesses like Walgreens drug stores for relief, she says customers have made comments such as, “This is why my package is not getting delivered. You’re in here shopping.” Now she sticks to a Carl’s Jr. fast food restaurant where she’s gotten to know the employees and won’t be harassed.

“The protections that workers need aren’t rocket science,” says Juanita Constible, a climate and health advocate at the Natural Resources Defense Council, who maintains a map of the sparse occupational health standards in US states. “We’re mowing the lawn at home, and we get too hot, so we take a break and drink a cup of water. But a lot of workers just don’t have that ability.” She says the US needs more legal protections for workers toiling in the heat.

A series of heat-related hospitalizations among UPS drivers last summer helped spur a bill in New York state to protect workers from extreme heat, says Charlene Obernauer, executive director of the nonprofit New York Committee for Occupational Safety and Health. The Temperature Extreme Mitigation Program, or TEMP Act, is modeled on standards in California and Washington and would require employers to provide training and protections such as water, shade, and extra breaks on days when temperatures exceed certain thresholds.

If passed by state lawmakers, the law would be the first in the nation to protect workers not just from extreme heat, but extreme cold. “You also have to look at how the winters are becoming more extreme, especially in upstate New York,” Obernauer says. She hopes it passes before the pendulum swings in the other direction.