The capital is set to see three days of heavy rain starting this morning.
Southwest England and Wales will also be hit with a yellow weather warning for rain today until tomorrow afternoon.
Weather warnings of heavy rain are in force across southern Scotland and northern England, including an amber alert for Cumbria which warns of “danger to life from fast flowing or deep floodwater”.
These areas could see a month’s worth of rainfall in one day, forecasters said.
Scotland has already been badly hit by the deluge, with two road bridges that spanned the River Annan in Dumfries and Galloway washed away on Thursday.
A cross-border rail line from Dumfries to Carlisle remains closed with trains unable to pass over a viaduct.
A major incident was declared in Hawick in the Scottish Borders with up to 500 properties feared to be at risk of flooding.