An urgent health warning has been upgraded as temperatures are set to soar to 33C.
The alert was raised on Friday as forecasters warned of the potential health implications of the prolonged period of hot weather.
The hot spell began on Friday, when parts of the UK were predicted to reach 28C by the afternoon, surpassing top European holiday destinations such as Saint-Tropez, Marbella and Santorini.
The Met Office has said it will start a consistent run of high temperatures over the next few days, meaning Britons could bask in an official heatwave.
Temperatures could dip slightly on Saturday before they begin to climb again on Sunday.
David Oliver, the Met Office’s deputy chief meteorologist, said: “The warm weather over much of England and Wales could last for much of next week.
“In the short term, many can expect temperatures in the mid to high 20C over the weekend, and then in the low 30C during the start of next week.
“Much of next week will remain warm for the time of year as well as dry and sunny for many areas.”
He said the warm spell will continue for southern and central areas into next week, with only a slight dip in top temperatures on Wednesday and Thursday before a possible move back to very high temperatures at the end of next week and the following weekend.
The level three heat health alert will be in place across London, the east of England and the southeast from 9am on Monday until 9am Friday.
The warning acknowledges the adverse impacts of high temperatures on people’s health and on infrastructure, such as the transport and energy sectors.
The Met Office defines a heatwave as when a location records a period for at least three consecutive days with daily maximum temperatures meeting or exceeding the heatwave temperature threshold.
The threshold varies by UK county.
Dr Agostinho Sousa, head of extreme events and health protection at the UK Health Security Agency (UKHSA), said: “We want everyone to enjoy the hot weather when it arrives, but also to check in on their vulnerable family, friends and neighbours to make sure they are prepared for the warm conditions ahead.
“High temperatures are predicted for a prolonged period, so make sure to follow our simple health advice to beat the heat, such as covering windows exposed to direct sunlight and making sure that fridges, freezers and fans are working properly.”
Sam Hughes, national water safety partner at the Royal National Lifeboat Institution (RNLI), added: “It is great to hear that the sun is on its way but we want to remind everyone to stay safe at the coast.
“If you are planning on going to the beach we would encourage you toâ¯visit a lifeguarded beach and swim between the red and yellow flags.
“If you get into trouble in the water, Float to Live: lean back, use your arms and legs to stay afloat. Control your breathing, then call for help or swim to safety. In a coastal emergency, call 999 or 112 for the Coastguard.”
Heatwaves are extreme weather events, but research shows climate change is making these events more likely, according to the Met Office.
The national weather service says heatwaves are 30 times more likely to occur now than before the industrial revolution because of the higher concentration of carbon dioxide in the atmosphere.
Heatwaves are predicted to become even more frequent, perhaps occurring as regularly as every other year by the 2050s.