Video: Heatwave signals a rail slow-down... but the sun won’t last

Temperatures will hit 31C (88F) in some parts of the country, beating the highs of 28C (82F) that made yesterday the hottest day of the year so far.

But by this evening the hot weather could be broken by thunder and showers.

Andy Murray, first on Wimbledon’s Centre Court today for a last-16 showdown with Frenchman Richard Gasquet, will be glad to play his match before the weather turns.

Andy Ratcliffe, a forecaster at MeteoGroup, the weather division of the Press Association, said: “Much of England will be hot and humid again. We’re looking at highs reaching about 31C (88F) in the London area.

“But there is the chance of scattered thundery showers developing, and there could be local downpours where they occur.”

Although some parts of Britain will enjoy soaring temperatures, some areas will be cooler than they were yesterday, he said.

“Further north-east across the UK it will be fresher, with bursts of rain. The rain will move from southern and eastern Scotland into northern England and into Wales by the end of the day.

“The remaining parts of Scotland and Northern Ireland will be mainly dry but fresher than yesterday.”

The weather will start to turn cooler tomorrow, with London enjoying the highest temperatures, of around 24C (75F).

Mr Ratcliffe said: “Tomorrow we will see the remaining hot and humid conditions clearing to leave all areas fresher for the rest of the week, with scattered showers.”

Earlier, Paul Mott of MeteoGroup, said there would be “heavy showers and localised thunder storms spreading east across England” this evening and tomorrow.

He added: “By Wednesday the heatwave will definitely be over. If anything it will be a bit colder than average, 20C (68F) in London and down to 15C (59F) elsewhere.”

Today’s high temperatures led to speed restrictions on a busy rail commuter route.

Speeds were reduced from 90mph to 80mph - and were later expected to go down to 60mph - on the London to Norwich Great Eastern line operated by the National Express East Anglia train company.

A Network Rail spokeswoman said: “We’re already doing weekend work on overhead wires on this route and the wires can overheat in very hot weather.

“A speed restriction has been introduced and it may be lowered to 60mph in the hottest part of the day.”

National Express East Anglia services were expected to be affected until 5pm today.

Between 12 noon and 5pm trains between London Liverpool Street station and Braintree in Essex will terminate at, and start from, Witham. A revised train service will run between Witham and Braintree.

Service alterations will be made on other East Anglia routes to and from Ipswich, Clacton-on-Sea, Colchester and Southend Victoria.