A heatwave is set to hit the UK, sending temperatures soaring into the 30s and triggering a health alert.
The Met Office said there was an “80% probability” of heatwave conditions between noon tomorrow and 6am on Thursday in parts of England.
Temperatures in the North East are expected to top 25C with bright and sunny conditions until Wednesday night.
Vulnerable people have been warned to stay indoors as temperatures in Britain soar above those in Rio de Janeiro.
The impending heatwave could see the mercury reach 35C on some parts of the UK (95F) on Wednesday, and temperatures are predicted to be high all week.
Social workers and other council staff have been placed on high alert to help those who might be struggling as temperatures soar.
Cllr Izzi Seccombe, of the Local Government Association, said: “The hundreds of deaths caused by extreme heat each year are avoidable. Councils are determined to reduce the toll as much as possible, but they cannot do it alone.
“Local people can make a massive difference by helping us identify other residents who might need some advice or practical help.”
The heatwave is being caused by a warm front and tropical continental air mass from Europe pushing across the country - bringing with it high temperatures and humidity.
However, severe thunderstorms are predicted to strike western and northern parts of Britain by Wednesday afternoon, and temperatures will dip on Thursday - but are likely to rise again before the weekend.
Dr Paul Cosford, director for health protection at Public Health England, said the high temperatures could be “dangerous” for vulnerable groups.
He said: “Older people and those with long-term illnesses are particularly vulnerable to the effects of very hot weather, so it’s important to look out for them - help them stay hydrated with plenty of cool drinks, and keep indoor areas as cool as possible.”
The medical director of West Midlands Ambulance Service, Dr Andrew Carson, warned that those with respiratory illnesses should stay indoors.
He said: “A prolonged heatwave poses a real danger to those patients with emphysema, asthma and long-term breathing problems.
“The hot weather makes breathing difficult, even for healthy individuals. That’s why we suggest people with respiratory illnesses should remain indoors as much as possible.”
The Met Office issued a Level 2 Heat-Health alert, warning that there is a 60% or greater chance of temperatures being high enough to affect health. The Met Office said the mercury could rise to 33C (91F) in London on Wednesday, and reach the high 20s in Scotland and northern England.
Paul Knightley, the forecast manager at MeteoGroup, said temperatures could reach 35C (95F) on Wednesday as the tropical continental air mass moves from north Africa, Spain and Portugal to Britain - possibly making it the hottest day for several years.
He also warned that the sun was “about as strong as it can be” and UV levels will be quite high.
He added: “One issue will be the temperatures won’t be dropping as low as perhaps we might normally expect overnight. Overnight temperatures in many areas might be 16-19C (60-66F), so the cumulative effect from day and night will actually be really hot.”
Heatwaves have been deadly in recent years. An ONS report found that the heatwave across Europe in August 2003 caused 2,091 excess deaths in England - particularly affecting over-75s in London.