At least 46 people died, trapped in a stifling semi trailer in San Antonio, along with 16 others suffering from heat exhaustion and heat stroke who were found Monday. This month is already the hottest June on record in San Antonio with 16 days so far hitting temperatures of 100°F or higher. Temperatures in the area hit 101°F on Monday, and the National Association of Medical Examiners has recommended that deaths where the body had a temperature of 105°F be certified as heat-related.

The 16 survivors, including four children, appear to have been so overcome by the heat they were unable to attempt to escape the trailer. The victims appear to have been attempting to migrate from Central America, including from Guatemala, the Texas Tribune reports, and possibly Honduras, according to the San Antonio News-Express, as well as Mexico. They were “families who were likely trying to find a better life,” San Antonio Mayor Ron Nirenberg told reporters.

Heat-related deaths along the U.S.-Mexico border are extremely common. At least 557 people died on the southwest border in the 12 months before last September 30 — more than 10 per week. A report published today in Environmental Research: Climate finds the human toll of climate change, especially from extreme heat, is vastly undercounted. (Texas Tribune, San Antonio Express-News, New York Times $, BBC; Heat-related death criteria and border deaths: NBC; Uncercounting: Bloomberg $; Climate Signals background: Extreme heat and heatwaves)