The United Farm Workers Union estimates that between 2005 and 2013, as many as 30 farmworkers died as a result of the heat in California. California law requires that workers have access to shade and water when temperatures rise to over 80 degrees, and are given frequent breaks when they go above 95 degrees. Many farmworkers who are undocumented are too afraid to speak out about their poor working conditions on the farm.
See "California Heat Puts Farm Workers at Risk", Anna North, September 4, 2015