The River Roding is continuing to rise very slowly, posing a risk of flooding to low-lying land, roads and gardens, the Environment Agency has said.
Surface water flooding from the river, which runs through Barking, can be expected in some locations.
The predicted heavy rain on Friday (31) afternoon is expected to increase the flood risk further.
The Environment Agency said it would continue to monitor the situation closely.
Another update will be given by the agency this evening.
There have been a number of alerts relating to the river over the last few months.
Since Christmas, there have been three warnings issued for the Lower River Roding, which meets the Thames in Barking.
For more information call Floodline on 0845 988 1188, select option 1 and enter Quickdial number 172915.
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