Heat health alerts across the UK have been extended through to midweek, with temperatures in the capital expected to climb into the low to mid-30s.
The Met Office has warned of potential health risks for vulnerable groups as the country faces its hottest spell of the year so far.
Concerns have also been raised over an increase in demand on health and care services, and overheated hospitals and care homes.
Amber alerts covering Yorkshire and the Humber, the East Midlands, West Midlands, East of England, London, South East and South West will now remain in place until 9am on Wednesday, the UK’s Health Security Agency has confirmed.
The North West is the only region in England to now have a yellow heat health alert. No alert is in place for North East England.
Health alerts serve to warn the public and provide guidance for NHS England, the government and healthcare professionals.
It comes as temperatures in London are forecast to reach highs of 34C on Monday and Tuesday, before falling to 26C by Wednesday.
Meanwhile, provisional data from the Met Office has suggested today has been the hottest start to the Wimbledon tennis championships ever.
It said “temperatures have risen to 29.7C at Kew Gardens", which is nearby in west London, making it "provisionally the warmest start to Wimbledon on record". The previous opening-day record of 29.3C set in 2001.
Conditions are expected to become more comfortable from midweek, with temperatures falling into the 20s.
Spectators queued from the early hours to enter the All England Club in southwest London, with many using fans, umbrellas and sunscreen to cope with the heat.
Vicki Broad, 57, a retired nurse from Swansea, who was the first person in the queue, said: "The sun has been tough but we're in the shade now."
Paul Jackson, from Stockport, said: "We were a bit worried about the heat, but it's been manageable."
"We've been drinking water, wearing hats, and making the most of the shade."
The competition has drawn crowds from across the globe, with some managing the weather better than others.
Maria Iniesta, 47, a physician from Madrid living in Houston, joked: "It's been funny to watch the British people sweating - it's been easy for us."
Met Office Chief Meteorologist Paul Gundersen said: "Temperatures are rising further today with low 30C widely across England including places like Manchester, Sheffield, Bristol and Cambridge.
"The highest temperature is expected to be 34C in London and the south east of England.
"These high temperatures and humid conditions will be quite uncomfortable for those working outside as well as people leaving Glastonbury and attending the start of Wimbledon and other outdoor events.
"Stay hydrated and try to keep out of the sun during the hottest part of the day," he advised.
Dr Agostinho Sousa, head of extreme events and health protection at UKHSA, said: "The current spell of hot weather is forecast to continue until the middle of this week, with temperatures above 30C likely in most regions of England.
"We are reminding everyone to take sensible precautions while enjoying the sun.
"Remember that it is very important to check on friends, family and neighbours who are more vulnerable, as the temperatures we are likely to see over the next few days can result in serious health outcomes across the population, especially for older adults or those with pre-existing health conditions."
