It’s 9.15 pm in San Antonio on 17 June. At this time, young children would usually be asleep and their parents enjoying a balmy summer’s evening. But not this year, when temperatures have reached triple figures in parts of Texas, and extreme humidity has made it feel hotter still, even after sunset.
Millions of people have been issued with excessive heat warnings and has claimed the lives of several people already. Temperatures peaked at 119F (48C), smashing countless high-temperature records across the state. More are expected to be broken in the coming week as the heatwave expands to the north and east.
These unusually-high temperatures have primarily been sparked by a ridge of high pressure parked over the Southern US called a “heat dome”, which occurs when the atmosphere traps hot ocean air like a lid.
At what point the heat becomes unbearable is personal, but a study published in 2010 estimated that a “wet-bulb” temperature of 95F (35C) at 100% humidity, or 115F at 50% humidity is probably as hot as most humans can maintain a healthy core body temperature by sweating. Above that “critical environmental limit” our body temperature rises continuously and the risk of heat-related illnesses such as heat stroke increases.
Read more at BBC.com