Air and rail passengers are being hit by more travel disruption even as temperatures cool after the hottest July day on record.
Flights from London airports, including Heathrow and Gatwick, have been delayed and cancelled due to heatwave-related issues technical problems with the UK’s air traffic control system.
It comes as the Met Office received a new provisional recording of 38.7C in Cambridge on Thursday, which – if confirmed – would be a new temperature record for the UK.
The railway network still faces heavy delays and cancellations after soaring temperatures caused overhead cables to sag. Great Northern, Thameslink and East Midland Trains are among the train companies affected with passengers advised to avoid travelling unless the journey is essential.
Meanwhile, the Met Office has issued a severe weather alert over the weekend warning of potential flooding in north, northeast, northwest and southeast England.
Follow our coverage of the day
Please allow a moment for the live blog to load
It is an exceptionally warm start to Friday after the hottest July day on record, the Met Office has said.
Train commuters face disruption after the extreme heat caused overhead cable to sag.
Thameslink will have a reduced ability to run trains, with half of its lines unavailable.
The rail network advises passengers to “delay your journey and refrain from travelling at this moment in time”.
The weather is also causing difficulties to flights as thunderstorms cause significant delays.
Flights were grounded at Heathrow, Stansted and Luton airports as a result of poor conditions across Europe on Thursday evening.
British Airways said that "severe thunderstorms are causing significant delays and cancellations to our operation in and out of London".
On the busiest day of the year for travellers, more than 100 flights have been cancelled to and from Britain’s airports, while on the railways passengers are still experiencing long delays and cancellations as a result of the extreme heat on Thursday.
British Airways has cancelled at least 50 flights to and from Heathrow airport – partly as a result of knock-on delays, but also to thin out the schedules and add resilience.
Multiple services to and from Berlin and Rome have been cancelled, along with domestic links to and from Manchester, Newcastle, Edinburgh and Aberdeen.
Read more here:
Thunderstorms in the south east of England are continuing to bring heavy rain, gusty winds and lightning this morning.
Last night, thunderstorms gave some impressive displays across parts of the country.
"The thunderstorms could continue on and off through the course of the day," Met Office meteorologist Greg Dewhurst said.
"There is enough energy in the atmosphere to keep it going."
The Met Office has issued a severe weather alert for tomorrow and Sunday, warning of potential flooding in north, north east and north west England.
The weather warning will be in force from 12pm tomorrow to 3pm on Sunday, although temperatures will still remain high today.
There is a small chance that homes and business could be flooded and a risk of cancellations to train and bus services, forecasters warn.
Gatwick airport has warned passengers to check with their airlines as “bad weather may cause some delays”.
Numerous travellers at Stansted also reported delays and cancellations, with the airport telling one passenger on social media that air traffic control restrictions over the south-east of England prompted the problems.
Crowds of passengers wait at Euston station in London after the extreme heat caused havoc on the rail network.
Rail companies feared trail lines would buckle, but it was sagging overhead cables which led to problems.
A busy Euston train station in London as morning train commuters face disruption (PA/Georgina Stubbs)
Great Northern, Thameslink and East Midlands Trains say services across their networks are still facing heavy delays and cancellations.
Passengers are advised to avoid travelling unless their journeys are essential.
Thameslink has warned passengers that if they decide to travel today, their journey will be extended by up to an hour.
Temperatures in Achnagart, northwest Scotland, fell to only 20.9C last night, breaking the Scottish record for the highest
Register for free to continue reading
Registration is a free and easy way to support our truly independent journalism
By registering, you will also enjoy limited access to Premium articles, exclusive newsletters, commenting, and virtual events with our leading journalists
Already have an account? sign in
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies