Oklahoma officials remain worried that drivers stuck on highways could be trapped in the path of dangerous twisters spawned by the violent thunderstorms hitting the US state.
A mother and baby - who are among five confirmed killed by the latest tornado - died when their car was flipped on Interstate 40.
Between 40 to 50 people are being treated for storm-related injuries, health officials have said.
Five patients, including a child, are in critical condition.
More top news
Temperatures will reach around 28 Celsius (82F) at their highest.
A minute's silence will be observed at 11am on Thursday in remembrance of those who lost their lives in the Manchester Arena attack.
New research has found those who consumed two cups had a 35% reduced risk, and for those who drank five cups, the risk halved.