The British Environment Agency has issued 16 severe flood warnings for areas where there is a danger to life.
Most of the warnings are along the River Thames, where the navy has been called in to help build flood defences.
Water levels are also rising in an area of Somerset in south-west England that has been flooded for weeks, the BBC reports.
More heavy rain and gale-force winds are expected over in the next few days.
Forecasters said Monday would be the driest day of the week, but rivers could continue to rise as previous rainfall works its way downstream.
Several Thames gauges are currently showing their highest water levels since being installed in the 1980s and 90s.
Water levels there are expected to rise despite the fact that significant rainfall is not expected during the day.
Armed forces personnel were in the heavily populated area on Sunday night building a 60cm defence to try to divert the river away from homes.