It has now extended yellow warnings for severe weather starting at 12:00 on Sunday until the end of Monday.
Where thunderstorms do develop, 20 to 30mm rain may fall locally in an hour, and close to 40mm of rain may fall in two or three hours, it said.
The Environment Agency's Dave Throup said there was the "potential for big storms for Sunday onwards as temperatures and humidity rise".
'It was like being in a washing machine'
A Staffordshire police officer has appeared on BBC TV this morning, talking again about the injuries she suffered when she had her legs crushed by dangerous driver who was trying to escape arrest.
PC Claire Bond told the BBC's Critical Incident "It was like I was in a washing machine, my body was like turning and then all of a sudden I felt quite a hard hit" and said she remember seeing her left leg pointing the wrong way and "my foot felt like jelly".
She was in hospital for nine days and her husband Darren, who is also a police officer, said he's had to take time off and stay at home to look after her.
PC Bond, who is determined to return to front-line policing, also said that when 25-year-old Gurajdeep Malhi, of Stafford was arrested, "relief that I felt was quite overwhelming".
He is due to be sentenced later this year after admitting causing grievous bodily harm with intent to avoid arrest, dangerous driving, driving while disqualified and driving without insurance.
Flooded road set to be cleared
BBC Radio Stoke
A road that flooded nine days ago is due to reopen today.
Sandon Road in Stafford should be cleared and opened later today, the county council said.
It has been closed in both directions between Astonfields and Peel Terrace.