A man and his two children were taken to hospital after being struck by lightning and several motorists were rescued from submerged cars as the UK was battered by torrential rain and thunderstorms.
The 37-year-old man and his five-year-old son were left critically ill after being hit outside a primary school in Northern Ireland.
The man's seven-year-old daughter was also seriously injured in the incident which happened shortly after 2pm on Tuesday as he collected his children from school.
Thunderstorms and lightning ripped across the UK throughout Tuesday afternoon, flooding roads, causing a temporary loss of power at Luton Airport, and setting alight trees, hoardings and telegraph poles.
In south London, 35mm of rain fell in the space of an hour causing three cars to become submerged in two metres of water.
Darlington Imoh was one of three drivers rescued from the flash flood in Sutton and said he feared he would drown before escaping through the window of his vehicle with the help of firefighters.
The 60-year-old said he "hugged and thanked" firefighters after they saved him.
He said: "I couldn't open the door because of the force of the water. I unwound the window and struggled out and then I was rescued by the fire brigade - that's why I am alive standing here now.
"It is the closest I got to death. Survival was my biggest concern, to survive."
London Fire Brigade said it had received more than 100 flood-related calls.
The Home Office said border security was not compromised after the loss of power at Luton Airport.
An airport spokesman said queues were longer than expected but terminal staff were helping passengers, fast-tracking anyone in special need and handing out drinking water.
Grahame Madge, forecaster for the Met Office, said the downpours could continue to cause localised flooding, surface water flooding and travel disruption.
