Flood alerts and severe weather warnings remain in place across parts of England and Wales as rescue services struggle with the number of emergency calls.
The fire service in West Sussex said their control room was dealing with "very high levels" of calls.
Roads in many parts of the south-west of the county were closed or impassable due to flooding, and people were being urged to travel only if "absolutely necessary".
Basement flats on Littlehampton seafront in West Sussex were evacuated after some properties were flooded by water up to 4ft (121cm) deep.
Flooding and standing water also led to accidents and severe disruption on the M25 between the A3 and M3 junctions.
The Environment Agency has issued five flood warnings - meaning flooding is expected - for the South East and one in the Anglian region.
It has also issued 43 alerts of potential flooding across the South East, three in the Anglian, two in the Southwest and Midlands and one in the Northeast region.
Sky News weather presenter Isobel Lang said: "The Environment Agency has issued amber warnings, which basically mean people should be prepared for potential flooding.
"Heavy rain and showers will continue in southern and southeastern areas through this evening and overnight, adding to the flood risk there.
In the west, there will be heavy showers for Ireland, Wales and the southwest, but many central and northern parts will be dry overnight, with cloud breaking and allowing temperatures to fall back into single figures."
The Met Office issued a severe weather warning for London and southeast England, and said people should be prepared for surface water flooding, difficult driving conditions and river flooding.
The latest warnings follow a weekend of heavy rain and flooding, mainly focused on Wales.
On Saturday, about 1,000 people were moved to safety from flooding in caravan parks and villages near Aberystwyth , with an estimated 150 rescued.
On Sunday villagers at Pennal , Gwynedd, were evacuated because of the risk of flooding from a reservoir.
They were later allowed to return after a controlled release of water from a disused quarry eased pressure on the reservoir wall.