Britain will experience a heatwave next week, the Met Office and the Department of Health said yesterday.
Temperatures could reach 3C (90F) in London on Monday and Tuesday, with other parts of the country also enjoying prolonged sunshine.
Night-time temperatures in London will fall no lower than 19C (66F). In other regions, daytime temperatures could reach 30C, with night-time temperatures staying above 15C (59F).
The East of England, South West, South East and Midlands will have the highest temperatures outside London. As a result of the forecast, the Met Office triggered 'Alert Level 2' of its Heatwave Plan – which means there is a 60 per cent risk of high temperatures in one or more regions on at least two consecutive days and during the night.
A spokesman for MeteoGroup UK, a private-sector forecasting company, said: "We are looking at a hot spell of weather coming in next week.
"The warm, humid air from the past couple of days is going to stagnate over the UK and the near continent, and will be coupled with strong sunshine and increasing humidity.
"It will become quite oppressive in places next week. There is also a growing risk of thunderstorms throughout the week." The Department of Health said people should take care as temperatures rise over the weekend and into Monday.
A spokeswoman 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 and remembering the needs of friends, relatives and neighbours is essential. Elderly people and those who are ill are particularly vulnerable during hot weather."