The Met Office has issued its first ever heatwave warning as forecasters predict temperatures to soar into the nineties this week.
Hospitals have been put on standby to deal with sunstroke victims and the government has urged the elderly and small children stay indoors as the hot and humid conditions reach potentially dangerous levels.
The mercury could hit a high of 91F (33C) by the middle of the week - and temperatures are expected to remain a warm and sticky 64F (18C) at night.
Southern England and the Midlands are expected to be hottest areas, but all parts of the country will see high levels of sunshine until next weekend. London is likely to be especially hot, meaning scorching conditions for Wimbledon fans players as the tournament goes into its second week.
A forecaster from the Met Office said: 'It is going to be the first significant heatwave since 2006. 'Temperatures will be in the low thirty degrees Celsius in many parts and somewhere is likely to hit 33 degrees sometime during the course of the week.
'With slack winds it's going to be very humid, although coastal areas will be a little fresher.'
The country is currently on amber level two of the Government's Heatwave Plan, but the Met Office expects it could reach level four by midweek - the highest level which denotes a state of emergency with the potential to cause water shortages or overwhelm the health service.
It is the first heat warning issued by the Met Office since the system was introduced two years ago.
A spokesman for the Department of Health said: 'The heat is especially dangerous for the very young, older people or those with serious illnesses. In particular, it can make heart and respiratory problems worse. In extreme cases, excess heat can lead to heat stroke, which can be fatal. Keeping the home as cool as possible during hot weather and remembering the needs of friends, relatives and neighbours who could be at risk is essential. Elderly people and those who are ill are particularly vulnerable during hot weather and the most oppressive conditions occur in our towns and cities. The Department of Health said children under four and elderly people were especially vulnerable, and should try to stay indoors where possible, especially during the hottest part of the day between 11am and 3pm.'
The last major heatwave to hit Britain was in 2003, when 2000 people died. A sweltering 102F (39C) was recorded in Brogdale in Kent on 10 August, a record high which still stands.
Tips of how to keep cool in the heatwave...
* People with serious health problems (for example heart conditions), should avoid going out in the heat, especially between 11am and 3pm.
* Drink cold drinks such as water or fruit juice regularly and avoid tea, coffee and alcohol.
* Stay tuned to the weather forecast and plan ahead with supplies - think of elderly neighbours who may need help.
* Keep plenty of water to hand and stay in the shade where possible.
* Identify the coolest room in the house to use as a room to cool down or sleep in.
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