Temperatures will soar this week as a heatwave continues – with a possible high of 33C (91.4F) forecast.
The mercury soared to 30.7C (87.2F) in Rostherne in Cheshire on Tuesday, beating Monday’s high of 30.1C (86.1F) in London, the Met Office said.
Public Health England (PHE) has issued a warning saying the extreme heat may pose a risk to the most vulnerable.
The rising temperatures have come with warnings to be careful near water and in the countryside, where fire crews have been tackling wildfires.
A search for missing 13-year-old Ryan Evans, who went missing after getting into difficulty in a lake in Stoke-on-Trent on Monday, will resume on Wednesday.
Surrey Police warned of the dangers of swimming in open water after the body of a man was recovered from a lake in Nutfield on Monday.
In York, police smashed the window of a vehicle in a hospital car park to rescue two dogs from sweltering conditions inside.
Parts of the UK are hotter than Athens in Greece, and on a par with Kuala Lumpur in Malaysia and Rio in Brazil.
The Met Office’s heat-health watch alert is currently at level two, meaning social and healthcare services are at the ready to reduce harm from a potential heatwave.
The RNLI has urged those heading to the seaside to seek out beaches with a lifeguard.
PHE said the over-65s, young children and those with health conditions are the most vulnerable in hot weather, and encouraged people to look out for each other.
Dr Thomas Waite of PHE said: “It’s vitally important that we keep an eye on friends, family and neighbours who may be at risk, and chances are we’ll all know someone, if we’re all going to stay well this summer.
Homeless people can also be vulnerable if exposed to strong sunshine and heat while sleeping rough, charity Evolve Housing + Support said.
Debra Ives, director of operations, said: “A lot of people sleeping rough don’t have the basic items needed to survive on the streets in hot temperatures.
“As a result, we’re calling on the public to donate things like sun cream, water, and sun hats, to help those at risk in the coming months.
“People can either offer them directly, or donate them to a shelter or charity.”
Temperatures are set to rise, with a possible high of 33C (91.4F) on Thursday, meteorologist Alex Burkill said, soaring above the UK average for this time of year of 17.3C (63.1F).
The fine, hot weather looks set to continue into next month, he added.
“At the moment it looks like that will be the general theme through much of July,” he said.
“Generally it looks like it will stay drier and warmer than average.”
Network Rail’s extreme weather action teams are being activated across the country to monitor “vulnerable locations”.
Services on the London Waterloo to New Malden line are being subjected to speed restrictions from 11am each day until Friday.
Network Rail said hot weather can cause the steel on rail lines to expand and in some cases buckle (curve), causing travel disruption.
Slower trains exert lower forces on the track, reducing the likelihood of buckling.