Residents in east London and Essex have been rescued from their cars after becoming trapped by water from flash floods.
A hospital building was also struck by lightning as extreme storms hit the south east.
Essex County Fire & Rescue Service received more than 100 calls to over 30 flooding incidents during a "very busy two-hour period" from 9.30pm last night after heavy rain hit the area.
Firefighters also rescued a motorist trapped in flood water under the A12 flyover in Rivenhall End this morning.
Elsewhere, crews were called in after a building at St Michael's Hospital, in Braintree, was struck by lightning.
The incident commander reported that there was a fire in the roof and the "entire" building - which measures 16 by six metres - was "completely smoke logged", the fire service said.
A spokesman for Mid Essex Hospital Services NHS Trust was unaware of the fire but said the hospital has a maternity unit.
The hospital has no inpatient wards, according to its website.
Since 6.30am the fire service has received dozens of calls to flooding and weather-related incidents.
Last night flash floods caused travel chaos across east London as downpours brought flooding to Tube stations and firefighters were called in to deal with the aftermath.
The London Fire Brigade said crews rescued three adults and two children from a flooded basement flat in Bethnal Green.
