From a Union Pacific train, a migrant woman texted a relative on Saturday. The railway car she was in felt very hot, she wrote. That day, the temperature in San Antonio, Texas, where the train was traveling, reached nearly 90 degrees Fahrenheit (32 degrees Celsius). Authorities estimate that the heat index inside the shipping containers could have reached as high as 140 degrees Fahrenheit (60 degrees Celsius). San Antonio police were alerted to …