So far, on the hottest day of the year, the country has basked in scalding temperatures of over 29 degrees Celsius (84.2 Fahrenheit).
A high of 29.3C (84.74F) was recorded at Heathrow and Kew Gardens in west London until 4:30 pm Thursday, surpassing the high of 28.2C (82.76F) recorded at Kew Gardens on Wednesday.
A sweltering 34C (93.2F) is expected in London and possibly parts of East Anglia on Friday, according to the Met Office.
Away from the capital and southeast, most of England and Wales are expected to experience 27-30°C, which means the country will be hotter than parts of Jamaica and the Maldives.
But experts, some of whom have linked the heat to climate change, are warning people of the dangers of hot weather.
Dr Radhika Khosla of the University of Oxford said: “The health implications of rising temperatures in the UK are serious.
“Important physiological changes occur in response to high temperatures, including changes in our circulatory, nervous and respiratory systems.
“When these adaptive measures are not enough, the risk of cardiopulmonary and cardiovascular diseases increases among the elderly, young children, people with chronic diseases, athletes and outdoor workers.
“Severe heat disrupts sleep, impairs cognitive function, and is associated with an increased risk of suicide or hospitalization due to mental illness.”
The UK Health Safety Agency (UKHSA) and the Met Office have issued a Level 3 Heat and Health Warning for London, the East of England and the South East.
This alert follows the Level 2 alert issued on Tuesday and confirms that the threshold temperatures set by the Met Office for the alert will be reached in three regions from Friday.
The Level 2 Warning remains in place for the East Midlands and South West.
Dr Vicki Thompson, climate scientist at the University of Bristol’s Cabot Environment Institute, said: “Heat waves are one of the deadliest natural hazards, with 3,000 deaths in the UK attributed to heat waves in 2021.
“Heat-related health problems include direct effects such as heat stroke and heart failure, and indirect effects including poor mental health and an increase in accidents such as car crashes and drownings.”
Dr Mark McCarthy, head of the Met Office’s National Climate Information Centre, said: “Reaching 34°C in June is a rare but not unprecedented event in historical climate data for the UK.
“But if it happened this week, it would be remarkable that it would have happened within three days during the last six of June.”
Professor Hanna Cloke of the University of Reading said: “Despite official warnings, some people still underestimate the impact of heat and don’t change their plans to take it into account.
“We need to consider how people are responding to current warnings and keep improving them. The warning system that people ignore is practically useless.
“Thousands of people are already dying due to excess heat in the UK and climate change will cause heatwaves to become more frequent and extreme in the future. Let’s not wait for people to die before taking heatwaves seriously.”
The UK’s highest recorded June temperature was 35.6°C at Southampton’s Mayflower Park in June 1976, and forecasters do not expect that high to be surpassed this week.