The longest heatwave for seven years is set to continue across Britain - but the blazing temperatures will bring widespread rain and thunderstorms next week.

Forecasters expect a slightly cooler weekend than in recent days, followed by a surge to 32C (89.6F) or possibly 33C (91.4F) in local areas on Monday and Tuesday.

The hot weather has taken its toll on the UK, with grass fires in London, mountain blazes in the Welsh valleys and forest fires in Fife, Scotland.

The heatwave is believed to have caused up to 760 premature deaths already, and the British Red Cross has launched two call centres in Norwich and Ipswich to check on the welfare of hundreds of elderly and vulnerable people in the region.

Britain will have a little respite from the extreme temperatures over the weekend, feeling fresher in eastern areas with more cloud and breezes coming in from the North Sea, weather experts said.

James Wilby, a forecaster with MeteoGroup, the weather division of the Press Association, said western Scotland, western Northern Ireland and the southern counties of England will be the hottest areas, with temperatures reaching 27C (80.6F) or 28C (82.4F), while eastern counties will see 22C (71.6F) or 23C (73.4F).

"Sunday will be warmer, with 29C in the southern counties, but Monday will be the warmest day, with 32C (89.6F) possible just south of London, and perhaps 33C (91.4F) in localised areas," Mr Wilby said.

"Tuesday will see similar conditions to Monday, but on Wednesday and Thursday it will be between 26C (78.8F) and 28C (82.4F)."

Showers and thunderstorms will hit the South West tomorrow, spreading through western parts of the UK on Monday. By Tuesday heavy, thundery rain will be more widespread, and thundery showers are expected to cover most of the country by Wednesday, Mr Wilby said.

Despite the prolonged heatwave, temperatures are unlikely to top the high of 36.5C (97.7F) recorded in Surrey in July 2006. The Met Office has warned of an "elevated risk" of fires in the countryside following six consecutive days of plus-30C temperatures and a dramatic reduction in the average monthly rainfall.