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A rare Level 2 heatwave warning has been issued by the Met Office following forecasts of unprecedented heat across the UK, expected to start tomorrow.

Weather experts believe that there is now a 80% probability of heatwave conditions between midday on Tuesday and 6am on Thursday in parts of England.

Brits are preparing for the hottest days of the year, starting from tomorrow and continuing on Wednesday, which is expected to have the highest temperature.

The weather is predicted to then cool from Thursday, as the warmest air gradually transfers eastwards.

Following the dramatic forecasts, Public Health England has issued a warning that the hot conditions could kill - with the very young and elderly particularly vulnerable.

Graham Bickler of Public Health England said: "There is considerable evidence that heatwaves are dangerous and can kill.

"In the 2003 heatwave, there were 2,000 to 3,000 excess deaths [more than usual] in England. Across Europe, there were around 30,000 excess deaths."

(Image: PA)

The health body is issuing advice on how to keep cool during the hot weather with its heatwave plan.

"Most of the information is common sense," says Bickler. "It's not rocket science, but it can have a dramatic effect."

Health issues that can arise from hot weather include:

Dehydration

Overheating

Heat exhaustion

Heatstroke

The weather could see thermometers rocket as high as 35C, and maybe even higher.

The UK is set to boast hotter weather than sunny hotspots such as Corfu, California, Florida and Hawaii.

The Level 2 alert - calling for "alert and readiness" - is the third-highest warning that can be issued.

(Image: Barcroft)

Level 3 is "heatwave action", while Level 4 is "national emergency".

Public Health England warns that the following people are most at risk:

older people, especially those over 75

babies and young children

people with a serious chronic condition, especially heart or breathing problems

people with mobility problems – for example, people with Parkinson's disease or who have had a stroke

people with serious mental health problems

people on certain medications, including those that affect sweating and temperature control

people who misuse alcohol or drugs

people who are physically active – for example, labourers or those doing sports

(Image: North Downs Picture Agency)

Clive James, Training Officer at St John Ambulance, says: "Extreme heat can be dangerous, particularly for the very young and old, but by being prepared you can spot the early warning signs and potentially be the difference between life and death in an emergency.

"Heat exhaustion and heat stroke are the most serious problems that can develop when the mercury soars so it’s essential that people can spot the signs, such as headache and dizziness, and get them somewhere cool and rehydrated as soon as possible."