The UK is set to experience its hottest day in 9 years - and there are numerous health worries

The sun rises over fishermen setting off for a day's fishing on the North Sea from Cullercoats on Tyneside
The sun rises over fishermen setting off for a day's fishing on the North Sea from Cullercoats on Tyneside

Urgent health warnings have been issued as Britain is set to experience its hottest day in nine years.

Temperatures could hit 35C (95F) in London today, while most of Britain will see the mercury hover between 30C (86F) and 33C (91.4C).

Young children, the elderly and those with serious illnesses are feared to be at particular risk amid the hot weather.

Wimbledon is braced for what could be the hottest day in its history, which may see its controversial new heat rule triggered which allows women, but not men, to take 10-minute breaks if a certain temperature is reached.

On the transport network, speed restrictions have been imposed by Network Rail on some train lines amid fears the metal tracks could buckle under the searing heat.

And fresh warnings about the dangers of outdoor swimming in the heat have been issued after a man's body was recovered from a reservoir.

The man was found at Alton Water reservoir in Tattingstone, Suffolk, at about 8pm yesterday.

Parts of the UK will be hotter than Barcelona and Athens.

British Coastguard teams have been handing out water to lorry drivers stuck in huge tailbacks on the M20 in Kent, caused by striking ferry workers who have closed the Port of Calais.

While Public Health England has warned people to try to keep out of the sun between 11am and 3pm, and have called on the public to look out for the elderly, young children and those with serious illnesses.

It has urged people to avoid physical exertion and drink plenty of water.

A spokeswoman for Network Rail warned that metal rail tracks can get 20C (68F) hotter than the air temperature, meaning they could reach 55C (131F) prompting fears the steel could expand and buckle.

A Network Rail spokeswoman said: "There will be speed restrictions in places, definitely. We are maintaining track temperatures and if necessary putting in speed restrictions so we can protect vulnerable places and keep the trains moving.

"There will be delays, but they might not be significant delays."

Employers have been urged to allow staff to travel outside rush hour to avoid overcrowded public transport during the exceptionally hot spell, now entering its third day.

Dr Angie Bone, head of extreme events at Public Health England (PHE) said: "During very hot weather, pregnant women and people who have chronic illnesses, including cardiovascular, respiratory, renal conditions, diabetes or Parkinson's disease, may experience discomfort if indoor temperatures are particularly hot and in using public transport.

"Employers should ensure indoor areas are kept cool and consider allowing these individuals to travel to or from their place of work during cooler, or less busy times of the day."

Greater Anglia Trains are handing out free bottled water to customers at all their major stations including Ipswich and Norwich.

Britain had the hottest day of the year so far yesterday, when temperatures reached 33C (91.4F) in Jersey and 30.5C (87F) in Northolt, west London.

The highest recorded July temperature was at Wisley, Surrey, in 2006, where the mercury peaked at 36.5C (98F).