BRITAIN is set for the hott­est day of the year so far with a sweltering high of 37C (99F) predicted - sparking a plague of rats, toxic air and even a shark "infestation" on the UK coastline.

Thermometers are expected to register 35C (95F) today as the longest scorcher since 1976 sizzles on and on.

25 Sun-seeker Scarlet Mitchell cools off in the sea at Woolacombe in Devon Credit: Apex News

25 National Women's Surf Champion Lucy Campbell, 23, enjoyed the hot weather at the Woolacombe beach in Devon Credit: SWNS:South West News Service

Summer heatwave 2018: Brits try to cool off in hot weather as record breaking temperatures hit Brighton beach

As temperatures continue to rise - and The Commons environmental audit committee said adapting to a warming climate was "a matter of life and death" - the red-hot heatwave has sparked a plague of rats.

Experts say numbers of the rodents have risen alarmingly in recent weeks as they gnaw on food rubbish warmed by weeks of sun, and early-ripened fruit.

And as MPs issued an alert over 7,000 heat-related deaths a year, forecasters say it may hit 37C (99f) on Friday for the hottest July day on record, beating the 36.7C (98F) set three years ago.

With the mercury rising, councils may step up household bin ­collections in a bid to battle the rising rat population, while Brits have also been told to not exercise outdoors.

25 The weather forecast for the next three days

25 Sun-seeker Scarlet splashes around in the ocean water Credit: Apex News

25 Some species of sharks are being spotted off our coasts for the first time Credit: Getty - Contributor

25 Hundreds of holidaymakers enjoy the sunshine and crystal clear waters at Porthcurno beach, Cornwall Credit: Neil Hope - The Sun

25 The weather has sparked a plague of rats after littered food has warmed Credit: Alamy

TOO HOT TO HANDLE: Britain ill-prepared to cope with heatwaves, MPs' report reveals Britain isn't ready to copy with heatwaves, an MPs' report reveals. The Commons environmental audit committee said adapting to warming climate was now "a matter of life and death". It warned that Britons would die in their thousands each year if homes and offices weren't brought in line to cope with the heat. They issued an alert over the 7,000 weather-related deaths that already occur. Roads and rail services let the country down, the report found, as none have been built to withstand heatwaves. MPs warned that by the 2040s, Britain could be hit with heatwaves every two years - causing a host of health problems. The report urges dress codes at school and work to be relaxed and a minister to be appointed to tackle the expected issues to come.

Rat expert Prof Steve Belmain said: “The heat is increasing the rodents’ activity. They can reproduce once a month — and transmit over 60 diseases.”

An explosion in rat numbers has been seen in Edinburgh, while Devon and inner city areas have also noted rising numbers.

One resident complained to Salford Council in Gtr Manchester: “Pink bins haven’t been collected for weeks — food rotting in this heat and there’s now rats! Not good enough.”

Nicola in Wigan tweeted: “Bins riddled with maggots and rats in the back alleys. It’s a health issue waiting to happen.”

25 A little girl enjoys a sunny day in Blackpool Credit: dave Nelson

25 A field fire near Drusillas Zoo Park

25 A woman prepares to take a morning swim in the Serpentine in London Credit: Reuters

25 Freya Keighley, six, pours water on Lil Heptinstall, 11, on St Anne's beach Credit: dave Nelson 07973697602

25 Holidaymakers and sun-seekers pack the huge beach at Woolacombe in Devon Credit: Apex News

25 Two women sunbathes in Hyde Park on Wednesday Credit: Alamy Live News

25 Stunning drone images has captured the effect the summer heatwave has had on Southsea's grassy areas Credit: Solent News

The country’s all-time temperature record could also be beaten if ­conditions are right, the Met Office said. That would mean topping the 38.5C (101C) recorded in Kent in August 2003.

Brits continued to lap up the summer sunshine on Wednesday, with many tucking into 99 Flake cornets beside the sea.

However, the warm weather isn't attracting just beach-goers.

The coastline is “infested” with sharks thanks to the hot weather, boatsmen warned.

25 Her friend Emily Manning also took a dip in the sea Credit: Apex News

25 A woman relaxes in the heat in Hyde Park Credit: Alamy Live News

25 A woman enjoyed the sunshine in Hyde Park on Wednesday afternoon Credit: Rex Features

Dozens of species not normally found in our waters are being spotted as sea temperatures rise, bringing predators closer to packed holiday beaches.

And boat operators say it will not be long before a Great White is in the English Channel.

Devon captain Ashley Lane told The Sun: “There’s no reason to suggest they’re not already here.”

Councils are now monitoring the temperatures to prevent illness under measures set out by Public Health England.

Met Office animated heat map video shows how temperatures will soar on Thursday and Friday

Demand for heat-related health advice from the NHS is soaring and visits to the NHS Choices website’s advice page for heat exhaustion and heatstroke more than quadrupled this month against July last year.

A Level 3 heat health watch alert co­v­ering a large part of England has been issued by the Met Office and Public Health England, warning people to stay out of the sun and keep homes as cool as possible.

Meanwhile if temperatures continue to soar, commuters on London’s Underground will have to be given free bottles of water.

Rail workers are also battling to stop tracks buckling — with the threat of speed restrictions loom­ing on Thursday and Friday.

TOXIC AIR ALERT: People warned not to exercise outdoors as London issues high air pollution alert BRITS have been warned not to exercise outdoors as London issues a "high" air pollution alert for today. As temperatures soar throughout the country amid a searing heatwave, the mercury is expected to push 35C by the end of the week. London Mayor Sadiq Khan said: "The heat, combined with London's toxic air, a lack of cloud cover and emissions travelling from the continent, means I am triggering a 'high' air pollution alert today, for tomorrow, under our comprehensive alert system. "This is the second time in six months that we have had to use the 'high' alert system and shows just why air pollution is a public health crisis." Air quality alerts will be displayed at bus stops, river piers, on busy roads and at the entrances to London Underground stations. In high pollution episodes, adults and children with lung problems and adults with heart problems should reduce strenuous physical exertion, particularly outdoors. People with asthma have been warned they might need to use their reliever inhaler more often, and older people should rest and not exert themselves. Anyone experiencing discomfort such as sore eyes, cough or sore throat should consider reducing activity, particularly outdoors.

25 A young boy cools off at the Jeppe Hein's Appearing Rooms Fountain in Central London Credit: Alamy Live News

25 A woman applies sun cream in Hyde Park, London, as the heatwave continues Credit: Alamy Live News

25 A woman relaxed and read a book on a deck chair in London on Wednesday Credit: Alamy Live News

25 Two young women enjoyed an ice cream in Hyde Park Credit: Alamy Live News

Tarmac roads can also melt once the temperature passes 33C (91F).

Firefighters in the capital say they have battled six times as many large grass fires this year as they did in the whole of 2017.

More than 260 crew were called out to deal with blazes on Monday night alone.

South Yorkshire firefighters dealt with over 500 calls between Monday and Wednesday morning, while West Midlands officers have also reported a “higher than expected” number of call-outs.

25 A woman sunbathes in Hyde Park on a very hot and humid day Credit: Alamy Live News

25 A woman stands in the shade in London Credit: PA:Press Association

People have also been told not to exercise outside amid a high pollution warning in London.

There have been warnings hundreds of people could die unnecessarily because of a lack of awareness of the rising risk of heatwaves.

An amber "heat health watch" warning remains in place for parts of England, with people being warned to try to stay out of the sun between 11am and 3pm.

Pet owners have been told not to exercise their dogs outside during the hottest parts of the day.

Nurses have warned that some hospital wards have reached more than 30C, leading to patients and relatives passing out or vomiting.

25 A person walks along a path on the fields above the White Horse of Westbury, Wiltshire, as the hot weather continues

25 A man swims past a swan on the Serpentine in London Credit: Reuters

Visitors were forced to evacuate Drusillas Zoo Park in East Sussex on Wednesday as a large fire broke out on dried grassland in a nearby field. No humans or animals were injured, the zoo said.

As temperatures soar on Friday, forecasters also say much of England could experience thunderstorms and hail showers, bringing the risk of flash floods.

The surge in rat numbers comes as the heat creates ideal conditions.

Kevin Higgins, a technical adviser for the British Pest Control Association, said: “There is an abundance of food available for rats at the moment.

Fruit is ripening earlier, people are dropping more waste and bins in public areas are overflowing.

More than 20 sharks arrive off coast of Cornwall and brave divers are swimming with them

“Normally during the summer months rats will disappear off into the fields. They haven’t needed to this year because the food’s right on their door-step. And when there’s more food, there’s more breeding.”

Prof Steve Belmain, a rat expert from the University of Greenwich, said the heatwave was playing a significant role.

He said: “The increased warmth is increasing their activity. When it’s warmer they have a higher metabolism and will need more food and water just to survive.

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“People are outdoors more and, the more we picnic, the more food waste we create.”

And he warned: “Rodents are known to transmit more than 60 different diseases.

“More diseases are coming from Europe. Climate change increases temperatures which means those diseases could establish themselves here in time.”