Session 2: Heat Stress

Voices from the Field

Asunción Valdivia, age 53, began working in California’s grape vineyards in mid-July 2004 where temperatures reached 104℉. He came up from Mexico to join his son, Luis. He was picking just four rows down from his son when Asunción collapsed. Other farm workers fanned him and put cool water on him while the crew boss’ daughter called 911. The dispatcher was not able to determine their location in the Giumarra Vineyards. Asunción came back to consciousness and the crew boss told his daughter to cancel the ambulance and for Luis to take him home. On the way home Asunción began to foam at the mouth and went limp. By the time Luis got him to the hospital he was dead. 

Heat is the leading weather-related killer in the U.S. and even more lethal to farm workers who are working under the hot sun for long hours. Heat has killed more than 780 workers across the country between 1992 and 2016, and seriously injured nearly 70,000 1. Unfortunately, these are just the reported cases, many do not seek medical care. Death is the most tragic result of heat exposure but symptoms can include headaches, nausea, dizziness, muscle cramps, weakness and irritability, confusion, slurred speech, seizures and loss of consciousness. Additionally, left untreated heat exposure can progress into acute kidney injuries and heat strokes. Heat exposure can also exacerbate other health problems such as asthma and heart disease. With accelerating climate change, worker injuries, as described, and deaths due to excessive heat exposure are projected to increase in the coming years. 

The solutions are simple, access to water, shade and rest. Most employers do not voluntarily provide access to these. Farm workers are often paid by piece rate which discourages them from taking breaks or stopping to hydrate. Luis reported that Giumarra Vineyards required a minimum of 15 boxes of grapes be picked before the first break at 9:30 am. At first he was picking fewer than seven boxes.

Additionally, farm workers often wear long-sleeve shirts to protect them from pesticide and sun exposure which further increases their body temperature. Working in fields, many farm workers are in direct sunlight with no access to shade while performing strenuous work. These things leave farm workers even more susceptible to heat stress. 

Unfortunately the end of the work day is not necessarily the end of the risk of heat stress for many farm workers. Worker housing often does not have air conditioning or fans. Farm workers experiencing heat stress do not have access to lower their body temperatures. A team of nursing staff from Emory University, with support from the Farmworkers Association of Florida, conducted a study in 2018 of heat stress in farm workers across Florida. They found that of the farm workers studied: 43% began the workday dehydrated, up to 72% showed signs of dehydration by the end of the workday; and more than 80% had dangerous body temperatures on at least one day of the three-day study 2. As temperatures continue to rise around the nation, it is crucial for regulations to be put in place. 

Asunción Valdivia’s death was preventable. As temperatures continue to rise with climate change we can anticipate that heat stress illnesses and deaths will continue to grow unless there is an intervention. Heat illness can be prevented by access to training, water, shade and rest breaks. But many employers will not provide these basic needs voluntarily, so federal legislation is needed. 


Support the “Asuncion Valdivia Heat Illness and Fatality Prevention Act” (HR3668) that requires the Occupational Safety and Health Administration (OSHA) to implement a national heat stress standard. 

Sign United Farm Workers’ Petition to demand better protections for those working in extreme heat.

Learn More

Download the Heat Stress Info Sheet.

See Farm Workers and the Envrionment: A Curriculum (pdf) Session 3: Heat Stress on page 13.

Read Farmworker Justice’s Fact Sheet on the “Asuncion Valdivia Heat Illness and Fatality Prevention Act”. 

Watch UC Davis’ Protecting Farm Workers as Temperatures Rise with Climate Change.

Read more about farm workers in Florida facing heat stress. 

Heat, Smoke and COVID Are Battering the Workers Who Feed America (New York Times)

Read more about Farm Workers and the Environment

Read more about Health and Safety issues affecting farm workers.


  1. Public Citizen et al (October 30, 2018). “Unworkable: Dangerous Heat Puts Florida Workers at Risk”. Public Citizen and Farmworker Association of Florida. Retrieved July 10, 2020. 
  2. Public Citizen et al (October 30, 2018). “Unworkable: Dangerous Heat Puts Florida Workers at Risk”. Public Citizen and Farmworker Association of Florida. Retrieved July 10, 2020.