The Met Office has warned that hot and humid weather will arrive today in the east of England, the south east, London and the east Midlands, which will all be put on heatwave level 2 status from this evening.
Temperatures are expected to reach around 28°C in the south east tomorrow, and London could see temperatures over 30°C, while night time temperatures are also looking warm with the south east dropping to just the high teens overnight, according to the Met Office's chief meteorologist, Paul Gunderson.
"The heat is expected to be more widespread both during the day and overnight on Wednesday, although peak temperatures probably not quite as high as on Tuesday," he said.
As such, Public Health England (PHE) has advised people to look out for others, especially older people, young children and babies and those with underlying health conditions.
This is the second health warning due to a heatwave that PHE has issued over the past three weeks.
"Much of the advice on beating the heat is common sense and for most people there’s nothing to really worry about," said Dr Thomas Waite, a member of the extreme events team at PHE.
"But for some people, such as older people, those with underlying health conditions and those with young children, summer heat can bring real health risks.
"To keep homes and sleeping areas cool at night remember to close curtains on windows that face the sun during the day, once the sun is off windows open them up to get a breeze and think about turning off electrical devices all over the home as they can generate unwanted heat too."
Dr Waite added: "Each year we hear stories of people who have fallen seriously ill because, even though it’s hotter, they may wear clothes which are too warm for hot weather, they may not drink enough or just try to do too much.
"By looking out for each other this summer we, health professionals, councils and the public, can all help each other stay well this summer."