"A bowing line of thunderstorms with embedded ... vortices will continue to pose a damaging-wind and tornado threat, with isolated large hail, as it crosses the watch area through the morning," the National Weather Service said.
A tornado-watch area extends over eastern central and northeast Oklahoma and northwest Arkansas, with forecasters urging residents to be prepared. It follows days of extreme weather with dozens of the storms touching down.
Please allow a moment for the live blog to load
Welcome to The Independent's live coverage of extreme weather in the Oklahoma and Arkansas regions on Tuesday.
The NOAA's Storm Prediction Centre has said that tornadoes are possible again today, along with damaging winds with gusts up to 75mph.
Hail could reach 2in in diameter, it added.
A confirmed tornado spawned over Tulsa International Airport in Oklahoma this morning, weather experts said.
Tulsa's National Weather Service outpost issued a string of warnings and urged people to seek shelter.
Flights at Tulsa were cancelled or altered, local reports said.
Storms deluged the area with rain, forcing authorities to close the Interstate 40 motorway due to high water.
Local news reports in Tulsa say public schools plan to open today but have delayed the start of classes due to the weather.
A house has collapsed in the north of the city, KJRH reported, while the area appears to have endured significant rainfall.
It came as the NWS announced a flash flood warning for northeast Oklahoma.
Most of Oklahoma is now suffering severe flooding, according to disaster relief officials.
The threat of severe storms continues for eastern Oklahoma and the weather systems will move into northwest Arkansas by about 10am local time, the NWS has said.
Some 22 million people are bracing for severe weather - if not tornadoes - across five states on Tuesday, according to the Reuters news agency.
It came as the worst US measles outbreak in 25 years spread to twister-hit Oklahoma, with 41 new cases nationwide.
Here's the latest from the NWS.
The NWS has issued a new tornado warning - meaning one has been sighted or found on radar - for Talihina, Clayton and Red Oak in Oklahoma.
Tulsa public transit is running more or less as usual bar a few diverted buses due to floods, authorities said.
But thousands of homes are without power.
Register for free to continue reading
Registration is a free and easy way to support our truly independent journalism
By registering, you will also enjoy limited access to Premium articles, exclusive newsletters, commenting, and virtual events with our leading journalists
Already have an account? sign in
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies