US cold snap: Why is Texas seeing Arctic temperatures?

Texas is known for its sprawling deserts and excruciating heatwaves - but right now, it's blanketed in a thick layer of ice.

The state is seeing some of its coldest temperatures in more than 30 years, with some areas breaking records that are more than a century old.

Parts of Texas hit 0F (-18C) on Sunday, and weather warnings are going to stay in place through the week.

So why is this normally boiling state suddenly freezing over?

According to the US National Weather Service (NWS), this is down to an "Arctic outbreak" that originated just above the US-Canada border.

Cold air outbreaks such as these are normally kept in the Arctic by a series of low-pressure systems, the NWS said. However this one moved through Canada and spilled out into the US last week.

The weather has already proven deadly. On Thursday, icy roads led to a massive crash involving more than 100 vehicles in Fort Worth, Texas, killing six people and leaving dozens more needing hospital treatment.

"The expansive dome of subfreezing temperatures across the northern tier of the country has laid the foundation for winter storms to wreak havoc from coast-to-coast, not only going into this weekend, but also into next week," the NWS said in a statement released on Friday.

Weather warnings for severe winter conditions are going to remain in place until at least Tuesday, when the weather system will begin to move north.

Marc Chenard, a forecaster from the service's Weather Prediction Centre, told Reuters that Amarillo in Texas will only see a high temperature of 2F (-17C), breaking the city's previous record of 12F (-11C) that was set in 1895.

Similarly Lubbock, Texas, will only reach a high of 9F (-13C). These temperatures, Mr Chenard said, are "40 to 50 degrees [Fahrenheit] below average".

Parts of Oklahoma and the Texas Panhandle are predicted to see as much as a foot of snow this week, while Dallas will have four inches.

Mr Chenard warns of more dangerous road conditions in Houston, caused by sleet and freezing rain.