With rivers bursting their banks and groundwater brimming at the surface, the additional rainwater will put additional pressure on the underground sewers which are already full.
The firm, which operates more than 67,000 miles of sewers, has been struggling in some areas to cope with the additional water filling up its pipes.
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Dry and sunny tomorrow and feeling warm.
Mild tonight with warm sunny spells and light winds tomorrow.
A section of the M3 has been closed and bomb disposal units are at the scene after reports of "potential hazardous material in the road".