Video footage shows severe flooding in Havering and Dagenham as a "tornado" struck Barking on Friday night.
Clips posted on Twitter show roads flooded with cars partially submerged in Gidea Park and surrounding areas.
Torrential rain caused the temporary closure both ways of the A12 Colchester Road (RM3) between Gallows Corner and Whitelands Way with heavy traffic around Roneo Corner.
Firefighters and a Barking and Dagenham Council Immediate Response Team assisted residents after the storm that struck at about 7pm in parts of Barking.
While Hulse Avenue, in Barking, felt the full force of the strong winds damaging roofs, toppling brick walls and causing tree damage, flash floods and heavy rain battered Collier Row, Harold Hill, Gidea Park and nearby areas.
Met Office forecaster Matthew Box said "it is probable that a brief tornado did occur".
A series of meteorological conditions are needed to create a tornado, including a funnel of cloud that reaches the ground, and these various factors have not been confirmed by experts.
Mr Box said: "The associated thunderstorms produced some very heavy and impactful rain over parts of north and east London and Essex which did result in flooding and travel disruption."
Some places are likely to have seen more than 40mm of rainfall in an hour.
Mr Box added that none of the Met Office's sites recorded the wind associated with the event, mainly because "it was on a small scale relatively speaking".
He said: "For those affected, there were very damaging winds."
The Met Office had issue a yellow thunderstorm warning on Friday evening which expired at 11pm.
There are about 35 tornadoes on average in the UK each year which would possibly cover "tens to hundreds of metres" and not be on the large scale that you might find in the US, Mr Box said.
Greater Anglia Rail reported delays of up to 20 minutes on trains travelling through Chadwell Heath and Brentwood because of the weather conditions last night
Do you have any pictures or video of the flooding in Havering or Dagenham or the "tornado" in Barking? Email michael.adkins@archant.co.uk
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