Temperatures continue to soar around the UK as forecasters anticipate what could be the hottest day on record.
The Met Office said the highest temperature reached so far on Wednesday was 33.7C at Cavendish in Suffolk.
But it says southern and eastern England could see a record-breaking 39C (102.2F) on Thursday, beating the all-time high of 38.5C from 2003.
Meanwhile, a body has been found after three people went missing in different parts of the River Thames on Tuesday.
Police believe it is a 23-year-old man who vanished while swimming with friends near Shadwell Basin in Wapping, east London.
The high temperatures have so far been concentrated in southern and eastern England. Writtle in Essex saw 33.5C, while the mercury rose to 32.4C at Heathrow and 31.9C at St James’s Park, London.
Northern Ireland and western Scotland have been the coolest areas with highs in the low 20s.
Forecasters say there was a 60% chance that the record for the highest temperature would be broken on Thursday.
The Met Office has also issued a yellow weather warning for thunderstorms which are expected to affect most of England and southern Scotland from 16:00 BST on Thursday and last into the early hours of Friday morning.
Thunderstorms swept across much of the UK on Tuesday night, with 48,000 lightning strikes reported.
The NHS has tweeted advice for dealing with the unusually hot temperatures and said: “Try to avoid spending extended periods in the sun this week. Also, be aware that vulnerable people are at increased risk of health issues.”
The London Ambulance service added: “If catching a train or the Tube in this hot weather make sure you carry a bottle of water and step off the train at the next station if you feel unwell.”
Councils have called on the public to check on family and friends, warning that the elderly and those with heart and respiratory problems were most at risk from the hot weather.
Network Rail has said speed restrictions may need to be introduced on Thursday “at vulnerable locations” to “reduce the likelihood of buckling”.
It advised passengers to check their trains before they travel.
Rail operator Southeastern has said it will run a “significantly reduced service” on Thursday due to the speed restrictions.
The Rail Delivery Group, which represents the industry, advised passengers in London and the South East to consider changing their travel plans on Thursday because of the expected heat.
Meanwhile, passengers on a Eurostar train travelling from Brussels to London were stranded in 38C on Wednesday morning, after their train broke down due to an overhead power supply problem.
The train was evacuated and passengers were given bottles of water while they waited for another train to collect them.
Eurostar advised people not to travel on its Brussels route because the power issue was causing “significant delays”, as well as some cancellations.
Belgium’s record temperature was broken on Wednesday when 39.9C was recorded as temperatures soared in Western Europe.
The town of Kleine Brogel in Limburg province hit 38.9C (102F), beating the previous record set in 1947.
The French city of Bordeaux also hit its highest temperature since records began, registering 41.2C (106.1F).
Lightning ‘like a gunshot’
People in parts of England and Wales are inspecting damage to their property following the fierce thunderstorms on Tuesday night.
One house in north Wales caught fire after being hit by lightning.
Megan Zahra, from Wrexham, said a lightning strike sounded “like a gunshot” when it set her bedroom roof on fire.
She woke up but thought it was a noise from outside and did not know the roof was on fire until her stepfather arrived to get her out.
Two lightning spotters had to be rescued from a beach in Middleton, near Morecambe, by police when their car got stuck amid a “spectacular” storm.