Two “large-scale” incidents took place in Upminster and Wennington on Tuesday, where black smoke billowed into the air and flames destroyed buildings and ravaged nearby fields.
A firefighter at the scene in Wennington, asked by the PA news agency what conditions were like, replied: “absolute hell”, while those affected by the blaze said it had been spreading “fast”.
Two people were also taken to hospital suffering smoke inhalation following a fire in Dagenham, with the full number of casualties unknown.
The all-time UK temperature record was broken on Tuesday, with the mercury soaring past 40C.
Conditions on grassland are tinder-dry, with fires creating additional hotspots of fire which affected sheds and further nearby properties.
Wennington residents described the blaze as their “worst nightmare”, with one family losing their home and life possessions.
Watch: Wennington resident says family 'lost everything' in fire
Locals were evacuated from their homes on Tuesday afternoon as black smoke billowed into the air while flames destroyed buildings and ravaged nearby fields.
A rescue centre for residents was set up at the Premier Inn on New Road.
One elderly woman was seen crying hysterically saying: “Oh my God – the house is gone”, while her family tried to comfort her.
Others were asking council and fire officials about whether their pets had been rescued and if their homes were still standing.
Major incidents were also declared by fire services in Norfolk and Suffolk as crews battled multiple blazes, with some of them starting in fields and spreading to houses.
Norfolk Fire and Rescue Service said on Tuesday evening that “all appliances are either committed to ongoing incidents or have been alerted to a state of stand-by for incoming calls”.
Firefighters in the county were called to more than 80 incidents on Tuesday, including one that started in a field in the village of Ashmanhaugh and spread to two homes.
In a further incident, a fire started in a field and spread to homes in the village of Ashill.
Suffolk Fire and Rescue Service also declared a major incident on Tuesday evening, and said it had been called to more than 60 incidents.
Of these, 38 were fires in the open, including large blazes in a field in the village of Campsea Ashe and at a park in Ipswich.
A major incident was declared in South Yorkshire after firefighters were called to multiple fires, including a number involving blazes spreading to houses.
The most serious blaze on Tuesday afternoon was in Barnsley when a row of houses in the Moorland Avenue area was consumed by flames.
Doncaster Council said a major blaze in Clayton also spread to three residential properties and there were reports of houses on fire in the Kiverton Park and Maltby areas of Rotherham.
There were also reports of a fire spreading to three houses in Kiverton Park, near Rotherham, and to garages and outbuildings on Sprotbrough Road, in Doncaster, where a number of homes were evacuated.
And a grass fire is also reported to have spread to houses in Maltby, near Rotherham.
Firefighters said they were also dealing with many less serious fires on fields throughout South Yorkshire, with many of these blazes leaving large plumes of smoke stretching across roads and villages.