Flooding in Shrewsbury could reach its “highest ever” level and close off the centre of the town, it has been warned.
Barriers have been put up, and a severe flood warning is in place, meaning there is a danger to life.
Shropshire Council closed many routes into and around Shrewsbury, and said flooding could seal off the town.
The Environment Agency (EA) said 40-50mm of rain had fallen over the Welsh mountains, and it was expected to cause problems further down the River Severn.
There are currently dozens of flood warnings and alerts in England after heavy rainfall.
Defences went up in Frankwell and Coleham Head in Shrewsbury overnight.
The EA’s Chris Bainger said they were predicting a water level of 4.8m to 5.2m.
“If we reach that [higher] level… then we’re above the highest that we’ve ever had,” he said.
Shropshire Council said businesses were open in Shrewsbury, but people would have to get to the centre on foot.
Clive Wright, from the authority, said staff have been out overnight warning residents at risk of flooding.
He said: “The river levels are set to rise during the day so we do expect that at some point today, we may get more flooding and if the barriers breach at Coleham again, as they did last week, then that will close off the town and the English Bridge.”
Telford & Wrekin Council workers have spent the night distributing sand bags in the Ironbridge area. Homes that are at risk in Jackfield were the first to receive help.
Shrewsbury Colleges Group said its English Bridge and Welsh Bridge campuses were closed on Monday, but its London Road campus would be open as usual.
Shrewsbury High School said its senior school would be closed on Monday, although the prep school would be open without a school minibus service.
Coleham Primary School School said it was planning to be open as normal. But Coalbrookdale and Ironbridge Church of England primary school was shut.