At least a dozen dead as heat dome bakes southern US

A migrant woman being treated for heat exhaustion in the Texas city of Eagle Pass on 26 June

At least a dozen people have died of heat-related causes in Texas and Louisiana as extreme temperatures continue to plague the country.

Eleven of the deaths took place in Texas' Webb County on the Mexican border, according to local officials.

Hundreds of other Texas residents have been sent to emergency rooms, breaking previous records.

The current weather is the result of a heat dome, in which high pressure is trapped because of wind patterns.

In Webb County - which is centred on the city of Laredo - the heat-related fatalities ranged in age from 60 to 80.

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"We don't see this in our county," county medical examiner Dr Corinne Stern said at a meeting of local officials on Tuesday.

"Laredo knows heat. Webb County knows heat. And I think our county was caught a little off guard.

"These are unprecedented temperatures here due to this dome of high pressure."

The dead have also included a man and his stepson, 14, who died while hiking in Texas' Big Bend National Park.

Statistics from the Centers for Disease Control and Prevention (CDC) shows that Texas averaged about 837 heat-related visits per 100,000 visits between 18 and 24 June, compared to about 639 during the same time period last year.

Two other deaths - a 62-year-old woman and a 49-year-old man - were also as a result of the heat in Caddo Parish, Louisiana, according to CBS, the BBC's US partner.

And five bodies were found in a busy human smuggling corridor in three parts of the New Mexico desert. Officials have not disclosed whether those deaths were directly attributable to the heat.

The current heat wave is the result of a relatively rare "heat dome", which only occurs every few years in the southern US. During a heat dome, high pressure is trapped in a particular area because of wind patterns, stretching 5 to 10 miles (8 to 16km) in altitude and across hundreds or thousands of miles horizontally.

Meteorologists expect the heat wave to continue to spread over the coming days, particularly in the southern US and Mississippi Valley.

Swathes of Texas, Louisiana, Arkansas, Alabama, Kansas and Missouri and other states continue to be under heat advisories. Hotter than average temperatures are also expected for the rest of the week in New Mexico, Georgia and Florida.

The heat has prompted warnings from the federal health officials and the National Weather Service that people in affected areas should limit outdoor activities and remain in air-conditioned areas as much as possible.

An average of 702 heat-related deaths occur in the US every year, according to CDC statistics, with nearly 68,000 people sent to emergency rooms.

Heatwaves have become more frequent, intense and last longer because of human-induced climate change, scientists say.

The world has already warmed by about 1.1C since the industrial era began and scientists project temperatures will keep rising unless governments around the world make steep cuts to emissions.