Oklahoma, northwest Texas and the Texas Panhandle are bracing for a day of extreme weather, including dangerous tornadoes, flooding and thunderstorms.
"Numerous intense and long-track tornadoes" are expected in the region today (May 20) and tonight, according to the National Weather Services' Storm Prediction Center (SPC).
There's a 95% chance of tornadoes, 95% chance of winds over 75 mph (120 km/h), and 95% chance of hail larger than 2 inches (5 centimeters), according to the SPC. [Tornado Facts: Causes, Formation & Safety]
The SPC officially issued a tornado watch across the region. About 5.5 million people live in the region likely to be affected by the weather system, CBS News reported.
"The only other watch like this was issued for Alabama on 27 April 2011," the SPC tweeted.
As CNN pointed out, today is the sixth anniversary of a tornado that struck the city of Moore, Oklahoma, killing 24 people.
"A tornado watch means that conditions are favorable for tornadoes to form during the next several hours," the SPC said, urging residents to pay attention to local media for updates. "If a tornado warning is issued for your area, move to a place of safety, ideally in a basement or interior room on the lowest floor of a sturdy building."
Tornadoes can continue to form and will remain a threat after dark. And serious weather remains a threat in the areas outside the immediate zone of highest risk.
"More isolated but still potentially dangerous severe weather, including tornadoes and destructive winds and hail, is possible in surrounding parts of Texas, Oklahoma, Kansas, and Arkansas," the SPC said.
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Originally published on Live Science.