A Level Two heatwave warning has been issued for the south east today, now officially the hottest day of the year, and health authorities are warning older and vulnerable people to stay safe.

London has today (June 24) hit 31C, and the Met Office is warning that temperatures will continue to rise sharply between today and 9pm on Friday.

A heat-health alert is place across large parts of the UK, as well as a level two heatwave alert in the south east, and the Met Office tweeted at 1pm that the hottest temperature of the year (31C) had been recorded at Heathrow Airport.

Please stay hydrated, wear sunscreen or stay in the shade as much as possible & look out for older or vulnerable people.

Public Health England are warning elderly people and those with health conditions to protect themselves amid "exceptionally hot weather forecast this week," and are urging people to keep an eye on them also.

Lewisham and Greenwich NHS Trust have also issued a warning, asking people to stay hydrated, wear sunscreen or stay in the shade as much as possible, and look out for older or vulnerable people.

Soaring temperatures have already seen the UK officially record its warmest day of the year so far, after the Met Office tweeted around 1pm that temperatures had reached 31C (87.8F) at Heathrow Airport.

It warned that conditions could get hotter still later in the afternoon.

Warnings have been issued about UV levels, which are going to be exceptionally high over the next few days, and health authorities are now encouraging people to keep an eye on the most vulnerable over the next few days.

Public Health England (PHE) said older people, those with underlying health conditions, and very young children - most of the people who have been shielding during lockdown - were all more at risk from the higher temperatures.

The amber level three requires social and healthcare services to target specific actions at high-risk groups, according to the Met Office website, and people are generally advised to keep cool and stay hydrated.

The heat alert is currently in place for the West and East Midlands, although temperatures across the south of England and London are expected to rise throughout the week and have already today hit 30C.

Emer O'Connell, consultant in public health at PHE, said it was important that people kept checking on the vulnerable, as many continued to spend more time at home due to coronavirus.

"You will need to do things differently this year, for example keeping in touch by phone," she said.

"If you need to provide direct care to someone at risk from hot weather, follow Government guidance on how to do this safely.

"The most important advice is to ensure they stay hydrated, keep cool and know how to keep their homes cool."

Health minister Jo Churchill said people could take simple steps to keep themselves safe.

She said: "Apply sunscreen regularly, stay hydrated, and protect your head from the sun.

"Look out for those who are vulnerable in the heat, and provide support where needed, continuing to follow social distancing guidance."

Advice from the Met Office included closing curtains on rooms that face the sun to keep indoor spaces cooler, avoiding excess alcohol and dressing appropriately for the weather.

St John Ambulance said this could mean wearing light clothes to keep your skin covered and protected in the sun, as well as wearing high-factor sunscreen.

Shoppers have also been advised to be aware they could be forced to spend extra time in the sun as a result of social distancing measures.

Dr Lynn Thomas, medical director at St John Ambulance, said: "Heat exhaustion and heatstroke are two of the most serious problems that can develop when the mercury soars but by being prepared you can spot the early warning signs, such as headache and dizziness."

London Fire Brigade (LFB) has warned people not to have barbecues on dry grass, not to drop cigarettes or matches, and not to leave rubbish such as glass bottles lying around amid a risk they could start fires.

Met Office meteorologist Alex Burkill said UV levels would reach eight across many places and get up to nine across parts of Devon and Cornwall.

He said: "That's about as high as it gets really in the UK.

"The sun is as strong as it gets at the moment because we're so close to the solstice.

"We've got peak sun strength, clear skies, plenty of sunshine - it's the perfect ingredients for high UV."

Tuesday was not quite the hottest day of the year, as the 28.6C (83.5F) recorded at Heathrow Airport and Kew Gardens fell short of the 28.9C (84F) recorded at the end of May.

Mr Burkill said the hottest day of the year would most likely come on Wednesday or Thursday.

He predicted temperatures would edge towards 33C (91.4F) as we experienced "lots of hot and sunny weather through the next couple of days".